Preamble formats for MIMO wireless communications

ABSTRACT

A method for generating a preamble of a frame for a multiple input multiple output (MIMO) wireless communication begins by, for each transmit antenna, generating a carrier detect field. The method continues by, for a first grouping of the transmit antennas, generating a first guard interval following the carrier detect field; and generating at least one channel sounding field. Continuing, the method applies cyclical shift prior to transmission via the first grouping of the transmit antennas. When the MIMO wireless communication includes more than the first grouping of the transmit antennas, for another grouping of the transmit antennas. For the another grouping of the transmit antennas, generating at least one other channel sounding field. The method proceeds by generating the first guard interval prior to the at least one other channel sounding field, and applying another cyclical shift prior to transmission via the another grouping of the transmit antennas.

CROSS REFERENCE TO RELATED PATENTS

The present U.S. Utility patent application claims priority pursuant to35 U.S.C. §120, as a continuation, to the following U.S. Utility patentapplication which is hereby incorporated herein by reference in itsentirety and made part of the present U.S. Utility patent applicationfor all purposes:

U.S. Utility Application Ser. No. 12/173,796, entitled “PREAMBLE FORMATSFOR MIMO WIRELESS COMMUNICATIONS,” , filed Jul. 15, 2008, now issued asU.S. Pat. No. 7,991,009, on Aug. 2, 2011, which claims priority pursuantto 35 U.S.C. 3 120, as a continuation, to the following U.S. UtilityPatent Application which is hereby incorporated herein by reference inits entirety and made part of the present U.S. Utility PatentApplication for all purposes:

2. U.S. Utility application Ser. No. 10/973,595, entitled “PREAMBLEFORMATS FOR MIMO WIRELESS COMMUNICATIONS,” filed Oct. 26, 2004, nowissued as U.S. Pat. No. 7,423,989, on Sep. 9, 2008, which claimspriority pursuant to 35 U.S.C. §119(e) to the following U.S. ProvisionalPatent Applications which are hereby incorporated herein by reference intheir entirety and made part of the present U.S. Utility PatentApplication for all purposes:

-   -   a. U.S. Provisional Application Ser. No. 60/544,605, entitled        “MULTIPLE PROTOCOL WIRELESS COMMUNICATIONS IN A WLAN,” , filed        Feb. 13, 2004, expired;    -   b. U.S. Provisional Application Ser. No. 60/545,854, entitled        “WLAN TRANSMITTER HAVING HIGH DATA THROUGHPUT,” , filed Feb. 19,        2004, expired;    -   c. U.S. Provisional Application Ser. No. 60/568,914, entitled        “MIMO PROTOCOL FOR WIRELESS COMMUNICATIONS,” , filed May 7,        2004, expired; and    -   d. U.S. Provisional Application Ser. No. 60/573/782, entitled        “PREAMBLE FORMATS FOR MIMO WIRELESS COMMUNICATIONS,” , filed May        24, 2004, expired.

TECHNICAL FIELD

The invention relates generally to wireless communication systems andmore particularly to supporting multiple wireless communicationprotocols within a wireless local area network.

DESCRIPTION OF RELATED ART

Communication systems are known to support wireless and wire linedcommunications between wireless and/or wire lined communication devices.Such communication systems range from national and/or internationalcellular telephone systems to the Internet to point-to-point in-homewireless networks. Each type of communication system is constructed, andhence operates, in accordance with one or more communication standards.For instance, wireless communication systems may operate in accordancewith one or more standards including, but not limited to, IEEE 802.11,Bluetooth, advanced mobile phone services (AMPS), digital AMPS, globalsystem for mobile communications (GSM), code division multiple access(CDMA), local multi-point distribution systems (LMDS),multi-channel-multi-point distribution systems (MMDS), and/or variationsthereof.

Depending on the type of wireless communication system, a wirelesscommunication device, such as a cellular telephone, two-way radio,personal digital assistant (PDA), personal computer (PC), laptopcomputer, home entertainment equipment, et cetera communicates directlyor indirectly with other wireless communication devices. For directcommunications (also known as point-to-point communications), theparticipating wireless communication devices tune their receivers andtransmitters to the same channel or channels (e.g., one of the pluralityof radio frequency (RF) carriers of the wireless communication system)and communicate over that channel(s). For indirect wirelesscommunications, each wireless communication device communicates directlywith an associated base station (e.g., for cellular services) and/or anassociated access point (e.g., for an in-home or in-building wirelessnetwork) via an assigned channel. To complete a communication connectionbetween the wireless communication devices, the associated base stationsand/or associated access points communicate with each other directly,via a system controller, via the public switch telephone network, viathe Internet, and/or via some other wide area network.

For each wireless communication device to participate in wirelesscommunications, it includes a built-in radio transceiver (i.e., receiverand transmitter) or is coupled to an associated radio transceiver (e.g.,a station for in-home and/or in-building wireless communicationnetworks, RF modem, etc.). As is known, the transmitter includes a datamodulation stage, one or more intermediate frequency stages, and a poweramplifier. The data modulation stage converts raw data into basebandsignals in accordance with a particular wireless communication standard.The one or more intermediate frequency stages mix the baseband signalswith one or more local oscillations to produce RF signals. The poweramplifier amplifies the RF signals prior to transmission via an antenna.

As is also known, the receiver is coupled to the antenna and includes alow noise amplifier, one or more intermediate frequency stages, afiltering stage, and a data recovery stage. The low noise amplifierreceives inbound RF signals via the antenna and amplifies then. The oneor more intermediate frequency stages mix the amplified RF signals withone or more local oscillations to convert the amplified RF signal intobaseband signals or intermediate frequency (IF) signals. The filteringstage filters the baseband signals or the IF signals to attenuateunwanted out of band signals to produce filtered signals. The datarecovery stage recovers raw data from the filtered signals in accordancewith the particular wireless communication standard.

As is further known, the standard to which a wireless communicationdevice is compliant within a wireless communication system may vary. Forinstance, as the IEEE 802.11 specification has evolved from IEEE 802.11to IEEE 802.11b to IEEE 802.11a and to IEEE 802.11g, wirelesscommunication devices that are compliant with IEEE 802.11b may exist inthe same wireless local area network (WLAN) as IEEE 802.11g compliantwireless communication devices. As another example, IEEE 802.11acompliant wireless communication devices may reside in the same WLAN asIEEE 802.11g compliant wireless communication devices. When legacydevices (i.e., those compliant with an earlier version of a standard)reside in the same WLAN as devices compliant with later versions of thestandard, a mechanism is employed to insure that legacy devices knowwhen the newer version devices are utilizing the wireless channel as toavoid a collision.

For instance, backward compatibility with legacy devices has beenenabled exclusively at either the physical (PHY) layer (in the case ofIEEE 802.11b) or the Media-Specific Access Control (MAC) layer (in thecase of IEEE 802.11g). At the PHY layer, backward compatibility isachieved by re-using the PHY preamble from a previous standard. In thisinstance, legacy devices will decode the preamble portion of allsignals, which provides sufficient information for determining that thewireless channel is in use for a specific period of time, thereby avoidcollisions even though the legacy devices cannot fully demodulate and/ordecode the transmitted frame(s).

At the MAC layer, backward compatibility with legacy devices is enabledby forcing devices that are compliant with a newer version of thestandard to transmit special frames using modes or data rates that areemployed by legacy devices. For example, the newer devices may transmitClear to Send/Ready to Send (CTS/RTS) exchange frames and/or CTS to selfframes as are employed in IEEE 802.11g. These special frames containinformation that sets the NAV (network allocation vector) of legacydevices such that these devices know when the wireless channel is in useby newer stations.

Both of the existing mechanisms for backward compatibility suffer from aperformance loss relative to that which can be achieved without backwardcompatibility and are used independently of each other.

Therefore, a need exists for a method and apparatus that enablesmultiple protocols to be supported within a wireless communicationsystem, including wireless local area networks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a wireless communication systemin accordance with the present invention;

FIG. 2 is a schematic block diagram of a wireless communication devicein accordance with the present invention;

FIG. 3 is a schematic block diagram of another wireless communicationdevice in accordance with the present invention;

FIG. 4 is a schematic block diagram of an RF transmitter in accordancewith the present invention;

FIG. 5 is a schematic block diagram of an RF receiver in accordance withthe present invention;

FIG. 6 is a schematic block diagram of an access point communicatingwith wireless communication devices in accordance with the presentinvention;

FIG. 7 is a diagram depicting one type of wireless communication inaccordance with the present invention;

FIG. 8 is a diagram depicting one type of MIMO wireless communication inaccordance with the present invention;

FIG. 9 is a diagram of a preamble of frame using cyclic shifting for twotransmit antennas in accordance with the present invention;

FIG. 10 is a diagram of a preamble of frame using sparse symbols and/ortones for two transmit antennas in accordance with the presentinvention;

FIG. 11 is a diagram of a preamble of frame using cyclic shifting forthree transmit antennas in accordance with the present invention;

FIG. 12 is another diagram of a preamble of frame using cyclic shiftingfor three transmit antennas in accordance with the present invention;

FIG. 13 is a diagram of a preamble of frame using sparse symbols and/ortones for three transmit antennas in accordance with the presentinvention;

FIG. 14 is a diagram of a preamble of frame using cyclic shifting forfour transmit antennas in accordance with the present invention;

FIG. 15 is another diagram of a preamble of frame using cyclic shiftingfor four transmit antennas in accordance with the present invention;

FIG. 16 is a diagram of a preamble of frame using sparse symbols and/ortones for four transmit antennas in accordance with the presentinvention;

FIG. 17 is a diagram depicting another type of wireless communication inaccordance with the present invention;

FIG. 18 is a diagram depicting another type of MIMO wirelesscommunication in accordance with the present invention;

FIG. 19 is a diagram of a preamble of frame using cyclic shifting fortwo transmit antennas using a legacy portion in accordance with thepresent invention;

FIG. 20 is a diagram of a preamble of frame using cyclic shifting forthree transmit antennas using a legacy portion in accordance with thepresent invention;

FIG. 21 is a diagram of a preamble of frame using cyclic shifting forfour transmit antennas using a legacy portion in accordance with thepresent invention;

FIG. 22 is a diagram of yet another wireless communication in accordancewith the present invention;

FIG. 23 is a diagram of yet another MIMO wireless communication inaccordance with the present invention;

FIG. 24 is a logic diagram of a method for multiple protocolcommunications in accordance with the present invention;

FIG. 25 is a logic diagram of a method for monitoring success ofwireless multiple protocol communications in accordance with the presentinvention;

FIG. 26 is a logic diagram of a method for a wireless communicationdevice to participate in a multiple protocol communication in accordancewith the present invention;

FIG. 27 is a logic diagram of another method for a wirelesscommunication device to participate in a multiple protocol communicationin accordance with the present invention;

FIG. 28 is a logic diagram of yet another method for a wirelesscommunication device to participate in a multiple protocol communicationin accordance with the present invention;

FIG. 29 is a diagram of simultaneous second channel sounding inaccordance with the present invention;

FIG. 30 is another diagram of simultaneous second channel sounding inaccordance with the present invention;

FIG. 31 is yet another diagram of simultaneous second channel soundingin accordance with the present invention; and

FIG. 32 is a further diagram of simultaneous second channel sounding inaccordance with the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Provided are preamble formats for MIMO wireless communications. In oneembodiment, a method for generating a preamble of a frame for a MultipleInput Multiple Output (MIMO) wireless communication begins by, for eachtransmit antenna of the MIMO wireless communication, generating acarrier detect field. The method continues by, for a first grouping ofthe transmit antennas of the MIMO wireless communication: generating afirst guard interval following the carrier detect field; and generatingat least one channel sounding field, wherein, from transmit antenna totransmit antenna in the first grouping, and wherein the at least onechannel sounding field follows the first guard interval, and applying acyclic shift prior to transmission. The method continues by, when theMIMO wireless communication includes more than the first grouping of thetransmit antennas, for another grouping of the transmit antennas:generating at least one other channel sounding field, wherein, fromtransmit antenna to transmit antenna in the another grouping, andwherein the at least one other channel sounding field follows the atleast one channel sounding field; and generating the first guardinterval prior to the at least one other channel sounding field, andapplying another cyclic shift prior to transmission for the anothergrouping of transmit antennas.

FIG. 1 is a schematic block diagram illustrating a communication system10 that includes a plurality of base stations and/or access points12-16, a plurality of wireless communication devices 18-32 and a networkhardware component 34. The wireless communication devices 18-32 may belaptop host computers 18 and 26, personal digital assistant hosts 20 and30, personal computer hosts 24 and 32 and/or cellular telephone hosts 22and 28. The details of the wireless communication devices will bedescribed in greater detail with reference to FIGS. 2 and/or 3.

The base stations or access points 12-16 are operably coupled to thenetwork hardware 34 via local area network connections 36, 38 and 40.The network hardware 34, which may be a router, switch, bridge, modem,system controller, et cetera provides a wide area network connection 42for the communication system 10. Each of the base stations or accesspoints 12-16 has an associated antenna or antenna array to communicatewith the wireless communication devices in its regional area, which isgenerally referred to as a basic service set (BSS) 9, 11, 13. Typically,the wireless communication devices register with a particular basestation or access point 12-14 to receive services from the communicationsystem 10. For direct connections (i.e., point-to-point communications),wireless communication devices communicate directly via an allocatedchannel to produce an ad-hoc network.

Typically, base stations are used for cellular telephone systems andlike-type systems, while access points are used for in-home orin-building wireless networks. Regardless of the particular type ofcommunication system, each wireless communication device includes abuilt-in radio and/or is coupled to a radio. The radio includes a highlylinear amplifier and/or programmable multi-stage amplifier as disclosedherein to enhance performance, reduce costs, reduce size, and/or enhancebroadband applications.

FIG. 2 is a schematic block diagram illustrating a wirelesscommunication device that includes the host device 18-32 and anassociated radio 60. For cellular telephone hosts, the radio 60 is abuilt-in component. For personal digital assistants hosts, laptop hosts,and/or personal computer hosts, the radio 60 may be built-in or anexternally coupled component.

As illustrated, the host device 18-32 includes a processing module 50,memory 52, radio interface 54, input interface 58 and output interface56. The processing module 50 and memory 52 execute the correspondinginstructions that are typically done by the host device. For example,for a cellular telephone host device, the processing module 50 performsthe corresponding communication functions in accordance with aparticular cellular telephone standard.

The radio interface 54 allows data to be received from and sent to theradio 60. For data received from the radio 60 (e.g., inbound data), theradio interface 54 provides the data to the processing module 50 forfurther processing and/or routing to the output interface 56. The outputinterface 56 provides connectivity to an output display device such as adisplay, monitor, speakers, et cetera such that the received data may bedisplayed. The radio interface 54 also provides data from the processingmodule 50 to the radio 60. The processing module 50 may receive theoutbound data from an input device such as a keyboard, keypad,microphone, et cetera via the input interface 58 or generate the dataitself. For data received via the input interface 58, the processingmodule 50 may perform a corresponding host function on the data and/orroute it to the radio 60 via the radio interface 54.

Radio 60 includes a host interface 62, digital receiver processingmodule 64, memory 75, a digital transmitter processing module 76, and aradio transceiver. The radio transceiver includes an analog-to-digitalconverter 66, a filtering/gain module 68, an IF mixing down conversionstage 70, a receiver filter 71, a low noise amplifier 72, atransmitter/receiver switch 73, a local oscillation module 74, adigital-to-analog converter 78, a filtering/gain module 80, an IF mixingup conversion stage 82, a power amplifier 84, a transmitter filtermodule 85, and an antenna 86. The antenna 86 may be a single antennathat is shared by the transmit and receive paths as regulated by theTx/Rx switch 73, or may include separate antennas for the transmit pathand receive path. The antenna implementation will depend on theparticular standard to which the wireless communication device iscompliant.

The digital receiver processing module 64 and the digital transmitterprocessing module 76, in combination with operational instructionsstored in memory 75, execute digital receiver functions and digitaltransmitter functions, respectively, in accordance with one or morewireless communication standards and as further function to implementone or more aspects of the functionality described with reference toFIGS. 3-11. The digital receiver functions include, but are not limitedto, digital intermediate frequency to baseband conversion, demodulation,constellation demapping, decoding, and/or descrambling. The digitaltransmitter functions include, but are not limited to, scrambling,encoding, constellation mapping, modulation, and/or digital baseband toIF conversion. The digital receiver and transmitter processing modules64 and 76 may be implemented using a shared processing device,individual processing devices, or a plurality of processing devices.Such a processing device may be a microprocessor, micro-controller,digital signal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on operationalinstructions. The memory 75 may be a single memory device or a pluralityof memory devices. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, and/or any device that storesdigital information. Note that when the processing module 64 and/or 76implements one or more of its functions via a state machine, analogcircuitry, digital circuitry, and/or logic circuitry, the memory storingthe corresponding operational instructions is embedded with thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry.

In operation, the radio 60 receives outbound data 94 from the hostdevice via the host interface 62. The host interface 62 routes theoutbound data 94 to the digital transmitter processing module 76, whichprocesses the outbound data 94 in accordance with a particular wirelesscommunication standard (e.g., IEEE 802.11 and versions thereof,Bluetooth and versions thereof, et cetera) to produce digitaltransmission formatted data 96. The digital transmission formatted data96 will be a digital base-band signal or a digital low IF signal, wherethe low IF typically will be in the frequency range of one hundredkilohertz to a few megahertz.

The digital-to-analog converter 78 converts the digital transmissionformatted data 96 from the digital domain to the analog domain. Thefiltering/gain module 80 filters and/or adjusts the gain of the analogsignal prior to providing it to the IF mixing stage 82. The IF mixingstage 82 converts the analog baseband or low IF signal into an RF signalbased on a transmitter local oscillation 83 provided by localoscillation module 74. The power amplifier 84 amplifies the RF signal toproduce outbound RF signal 98, which is filtered by the transmitterfilter module 85. The antenna 86 transmits the outbound RF signal 98 toa targeted device such as a base station, an access point and/or anotherwireless communication device.

The radio 60 also receives an inbound RF signal 88 via the antenna 86,which was transmitted by a base station, an access point, or anotherwireless communication device. The antenna 86 provides the inbound RFsignal 88 to the receiver filter module 71 via the Tx/Rx switch 73,where the Rx filter 71 bandpass filters the inbound RF signal 88. The Rxfilter 71 provides the filtered RF signal to low noise amplifier 72,which amplifies the signal 88 to produce an amplified inbound RF signal.The low noise amplifier 72 provides the amplified inbound RF signal tothe IF mixing module 70, which directly converts the amplified inboundRF signal into an inbound low IF signal or baseband signal based on areceiver local oscillation 81 provided by local oscillation module 74.The down conversion module 70 provides the inbound low IF signal orbaseband signal to the filtering/gain module 68. The filtering/gainmodule 68 filters and/or gains the inbound low IF signal or the inboundbaseband signal to produce a filtered inbound signal.

The analog-to-digital converter 66 converts the filtered inbound signalfrom the analog domain to the digital domain to produce digitalreception formatted data 90. The digital receiver processing module 64decodes, descrambles, demaps, and/or demodulates the digital receptionformatted data 90 to recapture inbound data 92 in accordance with theparticular wireless communication standard being implemented by radio60. The host interface 62 provides the recaptured inbound data 92 to thehost device 18-32 via the radio interface 54.

As one of average skill in the art will appreciate, the wirelesscommunication device of FIG. 2 may be implemented using one or moreintegrated circuits. For example, the host device may be implemented onone integrated circuit, the digital receiver processing module 64, thedigital transmitter processing module 76 and memory 75 may beimplemented on a second integrated circuit, and the remaining componentsof the radio 60, less the antenna 86, may be implemented on a thirdintegrated circuit. As an alternate example, the radio 60 may beimplemented on a single integrated circuit. As yet another example, theprocessing module 50 of the host device and the digital receiver andtransmitter processing modules 64 and 76 may be a common processingdevice implemented on a single integrated circuit. Further, the memory52 and memory 75 may be implemented on a single integrated circuitand/or on the same integrated circuit as the common processing modulesof processing module 50 and the digital receiver and transmitterprocessing module 64 and 76.

FIG. 3 is a schematic block diagram illustrating a wirelesscommunication device that includes the host device 18-32 and anassociated radio 60. For cellular telephone hosts, the radio 60 is abuilt-in component. For personal digital assistants hosts, laptop hosts,and/or personal computer hosts, the radio 60 may be built-in or anexternally coupled component.

Radio 60 includes a host interface 62, a baseband processing module 63,memory 65, a plurality of radio frequency (RF) transmitters 67, 69, 71,a transmit/receive (T/R) module 73, a plurality of antennas 81, 83, 85,a plurality of RF receivers 75, 77, 79, and a local oscillation module99. The baseband processing module 63, in combination with operationalinstructions stored in memory 65, execute digital receiver functions anddigital transmitter functions, respectively. The digital receiverfunctions include, but are not limited to, digital intermediatefrequency to baseband conversion, demodulation, constellation demapping,decoding, de-interleaving, fast Fourier transform, cyclic prefixremoval, space and time decoding, and/or descrambling. The digitaltransmitter functions include, but are not limited to, scrambling,encoding, interleaving, constellation mapping, modulation, inverse fastFourier transform, cyclic prefix addition, space and time encoding,and/or digital baseband to IF conversion. The baseband processingmodules 63 may be implemented using one or more processing devices. Sucha processing device may be a microprocessor, micro-controller, digitalsignal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on operationalinstructions. The memory 66 may be a single memory device or a pluralityof memory devices. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, and/or any device that storesdigital information. Note that when the processing module 63 implementsone or more of its functions via a state machine, analog circuitry,digital circuitry, and/or logic circuitry, the memory storing thecorresponding operational instructions is embedded with the circuitrycomprising the state machine, analog circuitry, digital circuitry,and/or logic circuitry.

In operation, the radio 60 receives outbound data 87 from the hostdevice via the host interface 62. The baseband processing module 63receives the outbound data 87 and, based on a mode selection signal 101,produces one or more outbound symbol streams 89. The mode selectionsignal 101 will indicate a particular mode as are indicated in modeselection tables. For example, the mode selection signal 101, withreference to Table 1 may indicate a frequency band of 2.4 GHz, a channelbandwidth of 20 or 22 MHz and a maximum bit rate of 54megabits-per-second. In this general category, the mode selection signalwill further indicate a particular rate ranging from 1megabit-per-second to 54 megabits-per-second. In addition, the modeselection signal will indicate a particular type of modulation, whichincludes, but is not limited to, Barker Code Modulation, BPSK, QPSK,CCK, 16 QAM and/or 64 QAM. As is further illustrated in Table 1, a coderate is supplied as well as number of coded bits per subcarrier (NBPSC),coded bits per OFDM symbol (NCBPS), data bits per OFDM symbol (NDBPS),error vector magnitude in decibels (EVM), sensitivity which indicatesthe maximum receive power required to obtain a target packet error rate(e.g., 10% for IEEE 802.11a), adjacent channel rejection (ACR), and analternate adjacent channel rejection (AACR).

The mode selection signal may also indicate a particular channelizationfor the corresponding mode which for the information in Table 1 isillustrated in Table 2. As shown, Table 2 includes a channel number andcorresponding center frequency. The mode select signal may furtherindicate a power spectral density mask value which for Table 1 isillustrated in Table 3. The mode select signal may alternativelyindicate rates within Table 4 that has a 5 GHz frequency band, 20 MHzchannel bandwidth and a maximum bit rate of 54 megabits-per-second. Ifthis is the particular mode select, the channelization is illustrated inTable 5. As a further alternative, the mode select signal 102 mayindicate a 2.4 GHz frequency band, 20 MHz channels and a maximum bitrate of 192 megabits-per-second as illustrated in Table 6. In Table 6, anumber of antennas may be utilized to achieve the higher bandwidths. Inthis instance, the mode select would further indicate the number ofantennas to be utilized. Table 7 illustrates the channelization for theset-up of Table 6. Table 8 illustrates yet another mode option where thefrequency band is 2.4 GHz, the channel bandwidth is 20 MHz and themaximum bit rate is 192 megabits-per-second. The corresponding Table 8includes various bit rates ranging from 12 megabits-per-second to 216megabits-per-second utilizing 2-4 antennas and a spatial time encodingrate as indicated. Table 9 illustrates the channelization for Table 8.The mode select signal 102 may further indicate a particular operatingmode as illustrated in Table 10, which corresponds to a 5 GHz frequencyband having 40 MHz frequency band having 40 MHz channels and a maximumbit rate of 486 megabits-per-second. As shown in Table 10, the bit ratemay range from 13.5 megabits-per-second to 486 megabits-per-secondutilizing 1-4 antennas and a corresponding spatial time code rate. Table10 further illustrates a particular modulation scheme code rate andNBPSC values. Table 11 provides the power spectral density mask forTable 10 and Table 12 provides the channelization for Table 10.

The baseband processing module 63, based on the mode selection signal101 produces the one or more outbound symbol streams 89 from the outputdata 88. For example, if the mode selection signal 101 indicates that asingle transmit antenna is being utilized for the particular mode thathas been selected, the baseband processing module 63 will produce asingle outbound symbol stream 89. Alternatively, if the mode selectsignal indicates 2, 3 or 4 antennas, the baseband processing module 63will produce 2, 3 or 4 outbound symbol streams 89 corresponding to thenumber of antennas from the output data 88.

Depending on the number of outbound streams 89 produced by the basebandmodule 63, a corresponding number of the RF transmitters 67, 69, 71 willbe enabled to convert the outbound symbol streams 89 into outbound RFsignals 91. The implementation of the RF transmitters 67, 69, 71 will befurther described with reference to FIG. 4. The transmit/receive module73 receives the outbound RF signals 91 and provides each outbound RFsignal to a corresponding antenna 81, 83, 85.

When the radio 60 is in the receive mode, the transmit/receive module 73receives one or more inbound RF signals via the antennas 81, 83, 85. TheT/R module 73 provides the inbound RF signals 93 to one or more RFreceivers 75, 77, 79. The RF receiver 75, 77, 79, which will bedescribed in greater detail with reference to FIG. 4, converts theinbound RF signals 93 into a corresponding number of inbound symbolstreams 96. The number of inbound symbol streams 95 will correspond tothe particular mode in which the data was received (recall that the modemay be any one of the modes illustrated in Tables 1-12). The basebandprocessing module 63 receives the inbound symbol streams 89 and convertsthem into inbound data 97, which is provided to the host device 18-32via the host interface 62.

As one of average skill in the art will appreciate, the wirelesscommunication device of FIG. 3 may be implemented using one or moreintegrated circuits. For example, the host device may be implemented onone integrated circuit, the baseband processing module 63 and memory 65may be implemented on a second integrated circuit, and the remainingcomponents of the radio 60, less the antennas 81, 83, 85, may beimplemented on a third integrated circuit. As an alternate example, theradio 60 may be implemented on a single integrated circuit. As yetanother example, the processing module 50 of the host device and thebaseband processing module 63 may be a common processing deviceimplemented on a single integrated circuit. Further, the memory 52 andmemory 65 may be implemented on a single integrated circuit and/or onthe same integrated circuit as the common processing modules ofprocessing module 50 and the baseband processing module 63.

FIG. 4 is a schematic block diagram of an embodiment of an RFtransmitter 67, 69, 71. The RF transmitter includes a digital filter andup-sampling module 475, a digital-to-analog conversion module 477, ananalog filter 479, and up-conversion module 81, a power amplifier 483and a RF filter 485. The digital filter and up-sampling module 475receives one of the outbound symbol streams 89 and digitally filters itand then up-samples the rate of the symbol streams to a desired rate toproduce the filtered symbol streams 487. The digital-to-analogconversion module 477 converts the filtered symbols 487 into analogsignals 489. The analog signals may include an in-phase component and aquadrature component.

The analog filter 479 filters the analog signals 489 to produce filteredanalog signals 491. The up-conversion module 481, which may include apair of mixers and a filter, mixes the filtered analog signals 491 witha local oscillation 493, which is produced by local oscillation module99, to produce high frequency signals 495. The frequency of the highfrequency signals 495 corresponds to the frequency of the RF signals492.

The power amplifier 483 amplifies the high frequency signals 495 toproduce amplified high frequency signals 497. The RF filter 485, whichmay be a high frequency band-pass filter, filters the amplified highfrequency signals 497 to produce the desired output RF signals 91.

As one of average skill in the art will appreciate, each of the radiofrequency transmitters 67, 69, 71 will include a similar architecture asillustrated in FIG. 4 and further include a shut-down mechanism suchthat when the particular radio frequency transmitter is not required, itis disabled in such a manner that it does not produce interferingsignals and/or noise.

FIG. 5 is a schematic block diagram of each of the RF receivers 75, 77,79. In this embodiment, each of the RF receivers includes an RF filter501, a low noise amplifier (LNA) 503, a programmable gain amplifier(PGA) 505, a down-conversion module 507, an analog filter 509, ananalog-to-digital conversion module 511 and a digital filter anddown-sampling module 513. The RF filter 501, which may be a highfrequency band-pass filter, receives the inbound RF signals 93 andfilters them to produce filtered inbound RF signals. The low noiseamplifier 503 amplifies the filtered inbound RF signals 93 based on again setting and provides the amplified signals to the programmable gainamplifier 505. The programmable gain amplifier further amplifies theinbound RF signals 93 before providing them to the down-conversionmodule 507.

The down-conversion module 507 includes a pair of mixers, a summationmodule, and a filter to mix the inbound RF signals with a localoscillation (LO) that is provided by the local oscillation module toproduce analog baseband signals. The analog filter 509 filters theanalog baseband signals and provides them to the analog-to-digitalconversion module 511 which converts them into a digital signal. Thedigital filter and down-sampling module 513 filters the digital signalsand then adjusts the sampling rate to produce the inbound symbol stream95.

FIG. 6 is a schematic block diagram of an access point 12-16communicating with wireless communication devices 25, 27 and/or 29. Thewireless communication devices 25, 27 and/or 29 may be any one of thedevices 18-32 illustrated in FIGS. 1-3. In this illustration, accesspoint 12-16 includes a processing module 15, memory 17 and a radiotransceiver 19. The radio transceiver 19 may be similar to the radiotransceiver of each wireless communication device in architecture andmay include a plurality of antennas, transmit paths and receive pathsfor multiple wireless communications within a proximal region or basicservice set. The processing module 15 may be a single processing deviceor a plurality of processing devices. Such a processing device may be amicroprocessor, micro-controller, digital signal processor,microcomputer, central processing unit, field programmable gate array,programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on operational instructions. The memory 17may be a single memory device or a plurality of memory devices. Such amemory device may be a read-only memory, random access memory, volatilememory, non-volatile memory, static memory, dynamic memory, flashmemory, cache memory, and/or any device that stores digital information.Note that when the processing module 15 implements one or more of itsfunctions via a state machine, analog circuitry, digital circuitry,and/or logic circuitry, the memory storing the corresponding operationalinstructions may be embedded within, or external to, the circuitrycomprising the state machine, analog circuitry, digital circuitry,and/or logic circuitry. The memory 17 stores, and the processing module15 executes, operational instructions corresponding to at least some ofthe steps and/or functions illustrated in FIGS. 7-32.

In this illustration, each of the wireless communication devices 25, 27and 29 utilize a different wireless communication protocol. Asillustrated, wireless communication device 25 utilizes protocol A 35,wireless communication device 27 utilizes protocol B 37 and wirelesscommunication device 29 utilizes protocol C 39. For example, protocolsA, B and C may correspond to different versions of the IEEE 802.11standard. In particular, protocol A may correspond to IEEE 802.11b,protocol B may correspond to IEEE 802.11g and protocol C may correspondto IEEE 802.11n.

The protocols may be ordered in accordance with a protocol orderingtable that has protocol A, protocol B and protocol C listed in order.The ordering may be based on the legacy of each of the correspondingprotocols where the first protocol in the ordering is the oldeststandard and the last entry in the protocol ordering is the most currentstandard. For example, in this present illustration protocol A maycorrespond to IEEE 802.11b, protocol B may correspond to IEEE 802.11gand protocol C may correspond to IEEE 802.11n. Alternatively, theprotocol ordering may be based on a user defined and/or systemadministrator defined procedure. For instance, if an unacceptable numberof transmission errors occur due to non-recognition of frames whileutilizing protocol A to set-up wireless communications, the user mayselect the protocol B format for setting up a wireless communication.This concept will be described in greater detail with reference to theremaining figures.

In operation, the access point 12-16, and/or each of the wirelesscommunication devices 25, 27 and 29, determine the protocol utilized byeach of the wireless communication devices within the proximal region.Recall that the proximal region may include a basic service set and/orneighboring basic service sets and/or a direct, or ad-hoc networkwherein the wireless communication devices communicate directly. Oncethe protocol of each of the wireless communication devices has beendetermined, the access point 12-16 and/or the wireless communicationdevices 25-29 determine, based on the protocol ordering, which protocolwill be utilized to set-up a wireless communication. For instance, ifprotocol A corresponds to IEEE 802.11b, the communication devices willutilize a MAC level protection mechanism to set-up a wirelesscommunication, as will be further described with reference to FIG. 22.As such, each of the wireless communication devices will utilizeprotocol A to set-up, or establish, a wireless communication such thatthe legacy devices recognize that a wireless communication is beingset-up and also recognizes the duration of that wireless communicationsuch that it will not transmit during that time, thus avoiding acollision.

Once the wireless communication is established, or set-up, utilizing aselected protocol (e.g., protocol A) from the protocol ordering, thecommunication device then utilizes its protocol to transmit the data forthe remainder of the wireless communication. For example, wirelesscommunication device 25 will utilize protocol A to establish and totransmit data for a wireless communication. Wireless communicationdevice 27 will utilize protocol A to set-up a wireless communication andthen use protocol B for the corresponding data transmission of thewireless communication. Similarly, wireless communication device 29 willutilize protocol A to establish, or set-up, the wireless communicationand then use protocol C for the data transmission portion of thewireless communication.

As one of average skill in the art will appreciate, if the proximalregion only includes wireless communication devices that utilize thesame protocol, the set-up and data transmission is done using thatprotocol. As one of average skill in the art will further appreciate, ifonly two different protocols are present within the proximal region, thelegacy protocol will be selected as the set-up protocol.

FIG. 7 is a diagram depicting a wireless communication between twowireless communication devices 100 and 102 that are in a proximal regionwhere the only protocol that is used is IEEE 802.11n. The wirelesscommunication may be direct (i.e., from wireless communication device towireless communication device), or indirect (i.e., from a wirelesscommunication device to an access point to a wireless communicationdevice). In this example, wireless communication device 100 is providingframe 104 to wireless communication device 102. The frame 104 includes awireless communication set-up information field 106 and a data portion108. The wireless communication set-up information portion 106 includesa short training sequence 157 that may be 8 microseconds long, a 1^(st)supplemental long training sequence 159 that may be 4 microseconds long,which is one of a plurality of supplemental long training sequences 161,and a signal field 163 that may be 4 microseconds long. Note that thenumber of supplemental long training sequences 159, 161 will correspondto the number of transmit antennas being utilized for multiple inputmultiple output radio communications.

The data portion of the frame 104 includes a plurality of data symbols165, 167, 169 each being 4 microseconds in duration. The last datasymbol 169 also includes a tail bits and padding bits as needed.

FIG. 8 is a diagram depicting a wireless communication between twowireless communication devices 100 and 102 that are in a proximal regionwhere the only protocol that is used is IEEE 802.11n. The wirelesscommunication may be direct (i.e., from wireless communication device towireless communication device), or indirect (i.e., from a wirelesscommunication device to an access point to a wireless communicationdevice). In this example, wireless communication device 100 is providingmultiple frames 104-1, 104-2, 104-N to wireless communication device 102using multiple antennas #1-#N. Each of the frames 104-1, 104-2, 104-Nincludes a wireless communication set-up information field 106 and adata portion 108. The wireless communication set-up information portion106 includes a short training sequence 157 that may be 8 microsecondslong, a 1^(st) supplemental long training sequence 159 that may be 4microseconds long, which is one of a plurality of supplemental longtraining sequences 161, and a signal field 163 that may be 4microseconds long. Note that the number of supplemental long trainingsequences will correspond to the number of transmit antennas beingutilized for multiple input multiple output radio communications.

The data portion of the frame 104 includes a plurality of data symbols165, 167, 169 each being 4 microseconds in duration. The last datasymbol 169 also includes a tail bits and padding bits as needed.

In this instance, the preamble (sometimes referred to as “Greenfield”)is for the case when only 0.11n devices are present. Alternatively, itmay be used with legacy devices (0.11, 0.11a, 0.11b, and 0.11g) when MAClevel protection (RTS/CTS or CTS to self) is employed. (MAC levelprotection may also be used when legacy stations are not present toprotect very long bursts.)

The short training sequence 157 maybe the same as IEEE 802.11a for TXantenna 1. For antennas 2 to N, it is a cyclic shifted version of thesame sequence. In the preferred mode, the amount of cyclic shift perantenna is computed from (Antenna number−1)*800/N in nanoseconds. Thatis for 1 antenna the shift is zero. For 2 antennas, the shift is 0 nsfor antenna 1 and 400 ns. For 3 antennas, the shifts are 0, 250, and 500ns. For 4 antennas, the shifts are 0, 200, 400, and 600 ns. Theimplementation is most straightforward when the shifts are rounded tounits of 50 ns (the inverse of the symbol clock frequency). Shifts maybe implemented in either a forward or backward direction.

There are several possible implementations of the supplemental longtraining sequences 159, 161: (m=1). For this case, there will only beone long training sequence 159. For antenna 1, it will be the same asthe IEEE 802.11a long training sequence 159 but only 4 microsecondslong, including a 0.8 microsecond guard interval. For antennas 2 to N itis a cyclic shifted version of the same sequence. In the preferred mode,the amount of cyclic shift per antenna is computed from (Antennanumber−1)*4/N in microseconds. That is for 1 antenna the shift is zero.For 2 antennas, the shift is 0 ns for antenna 1 and 4 microseconds. For3 antennas, the shifts are 0, 2.65 microseconds, 5.35 microseconds. For4 antennas, the shifts are 0, 2, 4, and 6 microseconds. Once again, theimplementation is most straightforward when the shifts are rounded tounits of 50 nanoseconds (the inverse of the symbol clock frequency).Shifts may be implemented in either a forward or backward direction.

For (m=N), the number of training sequences is equal to the number oftransmit antennas. This is preferable to the (m=1) case because it willlead to less channel estimation error at the receiver, especially forlarge numbers of antennas. Thus, it is scalable. There are two possiblechoices of training sequence:

-   -   Zero space—In this case, sequences (1,1), (2,2), (3,3), . . . up        to (N,N) are the same as the IEEE 802.11a long training        sequence. All others (i.e. (1,2), (2,1), etc) are null—nothing        is transmitted during that time slot.)    -   Subchannel null—In this case, the set of sub-channels in the        training sequences is sub-divided by the number of transmit        antennas. Individual subsets are activated on each sub-training        interval.

Orthogonal sequences that are generated by multiplying the subcarriersof the IEEE 802.11a long training sequence by an m×m orthonormal matrix,such as the matrix, which generates a discrete Fourier transform.

FIG. 9 is a diagram of a preamble of a frame 104-1, 104-2 using cyclicshifting for two transmit antennas, where the communication devices arein a proximal area that only includes IEEE 802.11n compliant devices.The preamble is part of the wireless communication set up information106 and includes a short training sequence (STS) 157, a long trainingsequence (LTS) 159 and 161, a signal field (SIG 1) 224, and a data fieldor another signal field 228. For the first antenna frame 104-1, the STS157 is divided into two sets of symbols 232, 234. In one embodiment, theSTS 157 includes 10 symbols of 800 nanoseconds as per previous versionsof the IEEE 802.11x specification. The LTS 159 and 161 of the firstantenna frame 104-1 includes a double guard interval (GI2) 236 that maybe 1600 nanoseconds in duration and corresponds to the last 1600nanoseconds of the LTS 159 and 161 prepended to the LTS 159 and 161.

The LTS 159 and 161 of the first antenna frame 104-1 includes a twicerepeating long training sequence that may correspond to previousversions of the IEEE 802.11x specification and, wherein, tones of theLTS are divided into two sets 238, 240. The signal field 224 and theoptional second signal field 228 contain information as previouslydiscussed, which may be separated by guard intervals (GI) 220, 226.

The preamble 104-2 for the second antenna includes similar components tothe preamble of the first antenna, but with the STS 157 and/or LTS 159and 161 being cyclic shifted. As shown, the second set of symbols 234precedes, in time, the first set of symbols 232 in the STS 157, which isthe opposite of the timing sequence of the preamble for antenna 1. As isfurther shown, the STS 157 may include 10 symbols divided into two sets,where the first set 232 includes symbols 0-5 and the second set 234includes symbols 6-9. For the first antenna, the first set of thesymbols 232 precedes, in time, the second set 234, and for the secondantenna the second set 234 precedes, in time, the first set 232. In oneembodiment, the cyclic shift may be 400-1600 nanoseconds.

Each LTS pattern of the LTS field 159 and 161 may be divided into twosets 238, 240 as shown, where the first set of tones 238 precedes, intime, the second set of tones 240 for the first antenna frame 104-1 and,for the second antenna frame 104-2, the second set 240 precedes, intime, the first set 238. As such, the LTS 159 and 161 of the secondantenna frame 104-2 is a cyclic shifted representation of the LTS 159and 161 of the first antenna frame 104-1.

FIG. 10 is a diagram of a preamble of frames 104-1, 104-2 using adifferent form of cyclic shifting by using sparse symbols and/or tonesfor two transmit antennas, where the communication devices are in aproximal area that only includes IEEE 802.11n compliant devices. Thepreamble is part of the wireless communication set up information 106and includes a short training sequence (STS) 157, a long trainingsequence (LTS) 159 and 161, a signal field (SIG 1) 224, a data field oranother signal field 228, and two guard intervals 220, 226. In thisembodiment, the symbols of the STS 157 are divided into two sets 232,234. The first set 232 is included in the first antenna frame 104-1 andthe second set of symbols 2324 is included in the second antenna frame104-2. The figure includes an example of a dividing the symbols intosets 232, 234, where, in one embodiment, the STS 157 includes 10 symbolsas per previous versions of the IEEE 802.11x specification. The LTS 159and 161 of the first antenna frame 104-1 includes a double guardinterval (GI2) 236 that may be 1600 nanoseconds in duration andcorresponds to the last 1600 nanoseconds of the LTS prepended to theLTS.

The LTS 159 and 161 includes a twice repeating long training sequencethat may correspond to previous versions of the IEEE 802.11xspecification and, wherein, tones of the LTS are divided into two sets238, 240. The first set of tones 238 is included in the first antennaframe 104-1 and the second set of tones 240 is included in the secondantenna frame 104-2.

FIG. 11 is a diagram of a preamble of frames 104-1, -2, -3 using cyclicshifting for three transmit antennas, where the communication devicesare in a proximal area that only includes IEEE 802.11n compliantdevices. The preamble is part of the wireless communication set upinformation 106 and includes a short training sequence (STS) 157, a longtraining sequence (LTS) 159 and 161, a signal field (SIG 1) 224, a datafield or another signal field 228, and two guard intervals 220, 226. Forthe first antenna frame 104-1, the STS 157 is divided into three sets ofsymbols 250, 252, 254. In one embodiment, the STS 157 includes 10symbols of 800 nanoseconds as per previous versions of the IEEE 802.11xspecification, where, for example, the first set 250 includes symbols0-2, the second set 252 includes symbols 3-5, and the third set 254includes symbols 6-9. As one of ordinary skill in the art willappreciate, other groupings of the symbols may be used.

The LTS 159 and 161 of the first antenna frame 104-1 includes a doubleguard interval (GI2) 236 that may be 1600 nanoseconds in duration andcorresponds to the last 1600 nanoseconds of the LTS prepended to the LTS159 and 161. The LTS 159 and 161 includes a twice repeating longtraining sequence that may correspond to previous versions of the IEEE802.11x specification and, wherein, tones of the LTS are divided intothree sets 256, 258, 260. The signal field 224 and the optional secondsignal field 238 contain information as previously discussed.

The preambles for the second and third antenna frames 104-2, -3 includesimilar components to the preamble of the first antenna frame 104-1, butwith the STS 157 and/or LTS 159 and 161 being cyclic shifted. As shown,the three sets of symbols 250, 252, 254 are shifted, in time, withrespect to each antenna frame 104-1, -2, -3. In one embodiment, thecyclic shift may be 400-1600 nanoseconds.

Each LTS pattern of the LTS field 159 and 161 may be divided into threesets 256, 258, 260 as shown, where the first set of tones 256 precedes,in time, the second and third sets of tones 258, 260 for the firstantenna frame 104-1, for the second antenna frame 104-2, the second set258 precedes, in time, the first and third sets 256, 260, and for thethird antenna frame 104-3, the third set 260 precedes, in time, thefirst and second sets 256, 258. As such, the LTS 159 and 161 of thesecond and third antenna frames 104-2, -3 is cyclic shifted with respectto the LTS 159 and 161 of the first antenna frame 104-1.

FIG. 12 is another diagram of a preamble of frames 104-1, -2, -3 usingcyclic shifting for three transmit antennas that include a legacyportion and a supplemental portion. The legacy portion includes the STS157, which may be divided into three sets of symbols 250, 252, 254, andan LTS section 159 and 161, which may be divided into two sets of tones238, 240. The supplemental section includes a guard interval 274 andonly one LTS pattern, which includes first and second set of tones 276,278.

In this embodiment, s1 . . . s2 are k*200 nanosecond cyclic shifts ofs0, where k=1 . . . 2 and s0-s2 correspond to the symbols of the STSfield 157 of the respective antenna frames 104-1, -2, -3. The first andsecond set of tones 238, 240 of the LTS 159 and 161 correspond to twolegacy IEEE 802.11a long training symbols (3.2 microsecond each plus 1.6microsecond prepended GI2 236), where each pairing of the first andsecond sets 238, 240 are equal. The first and second sets of tones 238,240 of the LTS 159 and 161 for the second antenna frame 104-2 are each1.6-microsecond cyclic shifts of the first and second sets of tones 238,240 for the first antenna frame 104-1. The supplemental LTS for thethird antenna frame 104-3 is a copy of the first and second sets 238,240 of one LTS pattern of the first antenna frame 104-1 with GI2 274(the last 1.6 microseconds) prepended. Only the first data symbol(DATA0) 272 has GI2 270 (the last 1.6 microseconds) prepended. Allsubsequent data symbols have just GI (the last 800 nanoseconds)prepended. The GI2 fields 274 prior to the supplemental LTS and GI2field 270 prior to the first data symbol (DATA0) are used to allowsettling of the power amplifiers.

FIG. 13 is a diagram of a preamble of frame using a form of cyclicshifting that includes sparse symbols and/or tones for three transmitantenna frames 104-1, -2, -3, where the communication devices are in aproximal area that only includes IEEE 802.11n compliant devices. Thepreamble is part of the wireless communication set up information 106and includes a short training sequence (STS) 157, a long trainingsequence (LTS) 159 and 161, a signal field (SIG 1) 224, a data field oranother signal field 228, and two guard intervals 220, 226. In thisembodiment, the symbols of the STS 157 are divided into three sets 280,282, 284. The first set 280 is included in the first antenna frame104-1, the second set of symbols 282 is included in the second antennaframe 104-2, and the third set of symbols 284 is included in the thirdantenna frame 104-3. The figure includes an example of a dividing thesymbols into sets, where, in one embodiment, the STS 157 includes 10symbols as per previous versions of the IEEE 802.11x specification. Insuch an example, the first set 280 may include symbols 0, 3, 6, thesecond set may include symbols 1, 4, 7, and the third set 284 mayinclude symbols 2, 5, 8.

The LTS 159 and 161 of the first antenna frame 104-1 includes a doubleguard interval (G12) 236 that may be 1600 nanoseconds in duration andcorresponds to the last 1600 nanoseconds of the LTS prepended to the LTS161. The LTS includes a twice repeating long training sequence 159 and161 that may correspond to previous versions of the IEEE 802.11xspecification and, wherein, tones of the LTS are divided into three sets286, 288, 290. The first set of tones 286 is included in the firstantenna frame 104-1, the second set of tones 288 is included in thesecond antenna frame 104-2, and the third set of tones 290 is includedin the third antenna frame 104-3. For example, if a long trainingsequence includes 15 tones, the first set 286 may include tones 0, 3, 6,9, 12, the second set 288 may include tones 1, 4, 7, 10, 13, and thethird set 290 may include tones 2, 5, 8, 11, 14.

FIG. 14 is a diagram of preambles of frames 104-1, -2, -3, -4 usingcyclic shifting for four transmit antennas. As shown, the STS 157 may bedivided into four sets of symbols 300, 302, 304, 306 and/or the LTS 159and 161 may be divided into four sets of tones 308, 310, 312, 314. Foreach antenna frame 104-1, -2, -3, -4, the set of symbols 300, 302, 304,306 are cyclically shifted and/or the set of tones 308, 310, 312, 314are cyclically shifted.

FIG. 15 is another diagram of preambles of frames 104-1, -2, -3, -4using cyclic shifting for four transmit antennas. In this embodiment, s1. . . s3 are k*200 nanosecond cyclic shifts of s0, where k=1 . . . 3,where s0-s3 correspond to the sets of symbols 300, 302, 304, 306 of theSTS 157. The LTS 159 and 161 and signal field 224 for the first andsecond antenna frames 104-1, -2 are as discussed with reference to FIG.12. The supplemental LTS for the third antenna frame 104-2 includes thefirst and second sets 238, 240, which may be copies of sets 238, 240 ofthe LTS 159 and 161 for the first antenna frame 104-1, with G12 236 (thelast 1.6 microseconds) prepended. The supplemental LTS for the fourthantenna frame 104-4 includes the first and second sets 230, 240 of theLTS for the second antenna frame 104-2 with G12 236 (the last 1.6microseconds) prepended. In other words, the LTS of the fourth antennaframe 104-4 is a 1.6-microsecond cyclic shift of the supplemental LTS ofthe third antenna. The first data symbol (DATA0) 272 has GI2 270 (thelast 1.6 microseconds) prepended. All subsequent data symbols have justGI (the last 800 nanosecond) prepended.

FIG. 16 is a diagram of a preamble of frame using a cyclic shifting thatuses sparse symbols and/or tones for four transmit antennas, where thecommunication devices are in a proximal area that only includes IEEE802.11n compliant devices. The preamble is part of the wirelesscommunication set up information 106 and includes a short trainingsequence (STS) 157, a long training sequence (LTS) 159 and 161, a signalfield (SIG 1) 224, a data field or another signal field 228, and twoguard intervals 220, 226. In this embodiment, the symbols of the STS 157are divided into four sets 320, 322, 324, 326. The first set 320 isincluded in the first antenna frame 104-1, the second set of symbols 322is included in the second antenna frame 104-2, the third set of symbols324 is included in the third antenna frame 104-3, and the fourth set ofsymbols 326 is included in the fourth antenna frame 104-4. The figureincludes an example of a dividing the symbols into sets, where, in oneembodiment, the STS includes 10 symbols as per previous versions of theIEEE.11× specification. For example, the first set 320 may includessymbols 0, 4, the second set 322 may include symbols 1, 3, the third setmay include symbols 2, 6, and the fourth set 326 may include symbols 3,7.

The LTS 159 and 161 of the first antenna frame 104-1 includes a doubleguard interval (GI2) 236 that may be 1600 nanoseconds in duration andcorresponds to the last 1600 nanoseconds of the LTS prepended to theLTS. The LTS includes a twice repeating long training sequence 159 and161 that may correspond to previous versions of the IEEE 802.11xspecification and, wherein, tones of the LTS are divided into four sets328, 330, 332, 334. The first set of tones 328 is included in the firstantenna frame 104-1, the second set of tones 330 is included in thesecond antenna frame 104-2, the third set of tones 332 is included inthe third antenna frame 104-3, and the fourth set of tones 334 isincluded in the fourth antenna frame 104-4. For example, if the longtraining sequence includes 20 tones, the first set 328 may include tones0, 4, 8, 12, 16, the second set 330 may include tones 1, 5, 9, 13, 17,the third set 332 may include tones 2, 6, 10, 14, 18, and the fourth set334 may include tones 3, 7, 11, 15, 19. Note that the supplemental LTSfields may be used such that the tones of an LTS pattern are onlydivided into two sets of tones.

FIG. 17 is a diagram of a wireless communication between two wirelesscommunication devices 100 and 102, each of which is compliant with IEEE802.11n. Such a communication is taking place within a proximal areathat includes IEEE 802.11n compliant devices, IEEE 802.11a compliantdevices and/or IEEE 802.11g compliant devices. In this instance, thewireless communication may be direct or indirect where a frame 110includes a legacy portion of the set-up information 112, remainingset-up information portion 114, and the data portion 108.

The legacy portion of the set-up information 112 includes a shorttraining sequence 157, which is 8 microseconds in duration, a longtraining sequence 171, which is 8 microseconds in duration, and a signalfield 173, which is 4 microseconds in duration. The signal field 173, asis known, includes several bits to indicate the duration of the frame110. As such, the IEEE 802.11a compliant devices within the proximalarea and the IEEE 802.11g compliant devices within the proximal areawill recognize that a frame is being transmitted even though suchdevices will not be able to interpret the remaining portion of theframe. In this instance, the legacy devices (IEEE 802.11a and IEEE802.11g) will avoid a collision with the IEEE 802.11n communicationbased on a proper interpretation of the legacy portion of the set-upinformation 112.

The remaining set-up information 114 includes additional supplementallong training sequences 159, 161, which are each 4 microseconds induration. The remaining set-up information further includes a high datasignal field 163, which is 4 microseconds in duration to provideadditional information regarding the frame. The data portion 108includes the data symbols 165, 167, 169, which are 4 microseconds induration as previously described with reference to FIG. 7. In thisinstance, the legacy protection is provided at the physical layer.

FIG. 18 is a diagram of a wireless communication between two wirelesscommunication devices 100 and 102, each of which is compliant with IEEE802.11n. Such a communication is taking place within a proximal areathat includes IEEE 802.11n compliant devices, IEEE 802.11a compliantdevices and/or IEEE 802.11g compliant devices. In this instance, thewireless communication may be direct or indirect where frames 110-1,110-2, 110-N each includes a legacy portion of the set-up information112, remaining set-up information portion 114, and the data portion 108using multiple antennas.

The legacy portion of the set-up information 112 includes a shorttraining sequence 157, which is 8 microseconds in duration, a longtraining sequence 171, which is 8 microseconds in duration, and a signalfield 173, which is 4 microseconds in duration. The signal field 173, asis known, includes several bits to indicate the duration of the frame110. As such, the IEEE 802.11a compliant devices within the proximalarea and the IEEE 802.11g compliant devices within the proximal areawill recognize that a frame is being transmitted even though suchdevices will not be able to interpret the remaining portion of theframe. In this instance, the legacy devices (IEEE 802.11a and IEEE802.11g) will avoid a collision with the IEEE 802.11n communicationbased on a proper interpretation of the legacy portion of the set-upinformation 112.

The remaining set-up information 114 includes additional supplementallong training sequences 159, 161, which are each 4 microseconds induration. The remaining set-up information further includes a high datasignal field 163, which is 4 microseconds in duration to provideadditional information regarding the frame. The data portion 108includes the data symbols 165, 167, 169, which are 4 microseconds induration as previously described with reference to FIG. 7. In thisinstance, the legacy protection is provided at the physical layer.

In one embodiment, m is the number of longer training sequences perframe, N is the number of transmit antennas, the preamble (sometimesreferred to as “Brownfield”) is for the case when 0.11a or 0.11g legacydevices present. The short training and long training sequences are thesame as IEEE 802.11a for TX antenna 1. For antennas 2 to N there are twopossibilities:

-   -   Use a cyclic shifted version of the same sequence. The amount of        cyclic shift per antenna is computed from (Antenna        number−1)*800/N in nanoseconds for the short training and        (Antenna number−1)*4/N in microseconds.    -   A second mode is to leave the short training through signal        field parts transmitted on antennas 2-to-N as null. (i.e. these        antennas do not transmit during this interval.) Furthermore,        supplemental long training sequences from antenna 1 are not used        and nothing is transmitted during this time.

The signal field 173 will follow the same format as IEEE 802.11a, exceptthe reserved bit (4) will be set to 1 to indicate an IEEE 802.11n frameand subsequent training for 0.11n receivers. The supplemental traininglong training sequences can be defined in multiple ways:

-   -   (m=1) For this case, there will only be one long supplemental        training sequence 159. It will be orthogonal to the IEEE 802.11a        long training sequence.    -   (m=N−1) For this case, the number of training sequences is equal        to the number of transmit antennas. This is preferable to the        (m=1) case because it will lead to less channel estimation error        at the receiver, especially for large numbers of antennas. Thus,        it is scalable.

There are three possible choices of training sequence:

-   -   Zero space—In this case, sequences (1,1), (2,2), (3,3), . . . up        to (m,m) are the same as the IEEE 802.11a long training        sequence. All others (i.e. (1,2), (2,1), etc) are null—nothing        is transmitted during that time slot.)    -   Subchannel null—In this case, the set of sub-channels in the        training sequences is sub-divided by the number of transmit        antennas. Individual subsets are activated on each sub-training        interval.

One embodiment uses Orthogonal sequences that are generated bymultiplying the IEEE 802.11a long training sequence by an m×morthonormal matrix, such as the matrix which generates a discreteFourier transform, as will be described in greater detail with referenceto FIGS. 29-32. For example, the 4 antenna case would employ thefollowing orthonormal matrix to generate the subcarriers for eachsupplemental long training sequence.

$\begin{matrix}{S_{k} = {\begin{bmatrix}s_{10,k} & s_{11,k} & s_{12,k} \\s_{20,k} & s_{21,k} & s_{22,k} \\s_{30,k} & s_{31,k} & s_{32,k}\end{bmatrix} = \begin{bmatrix}s_{00,k} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot \theta_{k}}} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot \phi_{k}}} \\s_{00,k} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot {({\theta_{k}\frac{4 \cdot \pi}{3}})}}} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot {({\phi_{k}\frac{2 \cdot \pi}{3}})}}} \\s_{00,k} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot {({\theta_{k}\frac{2 \cdot \pi}{3}})}}} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot {({\phi_{k}\frac{4 \cdot \pi}{3}})}}}\end{bmatrix}}} \\{{\theta_{k} = {\pi \cdot {k/( {4 \cdot N_{subcarriers}} )}}}{\phi_{k} = {\pi \cdot {( {k + 4} )/( {2 \cdot N_{subcarriers}} )}}}}\end{matrix}$FIG. 19 is a diagram of preambles of frames 104-1, -2 using cyclicshifting for two transmit antennas using a legacy portion. The STS 157is divided into two sets of symbols 344, 346 as shown. For example, thefirst set 344 may include symbols 0-4, and the second set 346 mayinclude symbols 5-9. The next portion of the preamble for the firstantenna frame 104-1 includes a legacy LTS 340, guard interval 220, and asignal field 224. The supplemental LTS 342 for the second antenna frame104-2 is identical to the LTS of the first antenna frame, but shifted intime.

FIG. 20 is a diagram of preambles of frames 104-1, 104-2, 104-3 usingcyclic shifting for three transmit antennas using a legacy portion. TheSTS 157 is divided into three sets of symbols 250, 252, 254 as shown andas previously discussed. The next portion of the preamble for the firstantenna frame 104-1 includes a legacy LTS 340, a guard interval 220, anda signal field 224. The supplemental LTS 342 for the second antennaframe 104-2 is identical to the LTS of the first antenna frame, butshifted in time. The supplemental LTS for the third antenna frame 104-2is cyclic shifted version of the supplemental LTS of the second antenna.All three frames 104-1, -2, -3 further include a double guard interval336 and a data field 228.

FIG. 21 is a diagram of preamble of frames 104-1, -2, -3, -4 usingcyclic shifting for four transmit antennas using a legacy portion. TheSTS 157 is divided into four sets of symbols 300, 302, 304, 306 as shownand as previously discussed. The next portion of the preamble for thefirst antenna frame 104-1 includes a legacy LTS 340, a guard interval220, and a signal field 224. The supplemental LTS 342-1 for the secondantenna frame 104-2 is identical to the LTS of the first antenna frame104-1, but shifted in time. The supplemental LTS 342-1 for the thirdantenna frame 104-3 is cyclic shifted version of the supplemental LTS342-1 of the second antenna frame 104-2. The supplemental LTS 342-2 forthe fourth antenna frame 104-4 includes only one LTS pattern 264 of thelegacy LTS, is time shifted as shown, and is approximately 4μS induration.

FIG. 22 is a diagram of a wireless communication between two wirelesscommunication devices 100 and 102 that are both IEEE 802.11n compliant.The wireless communication may be direct or indirect within a proximalarea that includes IEEE 802.11 compliant devices, IEEE 802.11a, IEEE802.11b and/or IEEE 802.11g devices. In this instance, the frame 111includes a legacy portion of the set-up information 112, remainingset-up information 114 and the data portion 108. As shown, the legacyportion of the set-up information 112, or legacy frame, includes an IEEE802.11 PHY preamble (i.e., STS 157, LTS 171, and signal field 173) and aMAC partitioning frame portion 175, which indicates the particulars ofthis particular frame that may be interpreted by legacy devices. In thisinstance, the legacy protection is provided at the MAC layer.

The remaining set-up information 114 includes a plurality ofsupplemental long training sequences 159, 161 and the high data signalfield 163. The data portion 108 includes a plurality of data symbols165, 167, 169 as previously described.

FIG. 23 is a diagram of a wireless communication between two wirelesscommunication devices 100 and 102 that are both IEEE 802.11n compliantusing multiple antennas. The wireless communication may be direct orindirect within a proximal area that includes IEEE 802.11 compliantdevices, IEEE 802.11a, IEEE 802.11b and/or IEEE 802.11g devices. In thisinstance, each of the frames 111-1, 111-2, 111-N includes a legacyportion of the set-up information 112, remaining set-up information 114and the data portion 108. As shown, the legacy portion of the set-upinformation 112, or legacy frame, includes an IEEE 802.11 PHY preamble(i.e., STS 157, LTS 171, and signal field 173) and a MAC partitioningframe portion 175, which indicates the particulars of this particularframe that may be interpreted by legacy devices. In this instance, thelegacy protection is provided at the MAC layer. Note that the fieldsfollow the same structure as for FIGS. 9 and 10 described above, withthe exception of the signal field. This is an alternative that uses MACpartitioning to set the NAV of legacy stations. The MAC partitioningsegment contains frame information, coded at a legacy rate to allowreception by IEEE 802.11a and IEEE 802.11g stations. The definitions ofthe supplemental long training symbols 159, 161 follows the same formatas in the previous FIG. 9.

The remaining set-up information 114 includes a plurality ofsupplemental long training sequences 159, 161 and the high data servicefield 163. The data portion 108 includes a plurality of data symbols165, 167, 169 as previously described.

FIG. 24 is a method for multiple protocol wireless communications in aWLAN. The method begins at step 120, where an access point (for indirectwireless communications) or a wireless communication device (for directwireless communications), determines protocols of wireless communicationdevices within a proximal region. In an embodiment, the protocols may bedetermined based on frequency band of use and wireless local areanetwork communication format of each of the wireless communicationdevices. For example, if the frequency band is 2.4 GHz, a device mayhave a WLAN communication format in accordance with IEEE 802.11b, IEEE802.11g, and/or IEEE 802.11n. If the frequency band is 4.9-5.85 GHz, adevice may have a WLAN communication format in accordance with IEEE802.11a or IEEE 802.11n. Further, the proximal region includes coveragearea of a basic service set, coverage area of an ad-hoc network, and/orcoverage area of the basic service set and at least a portion of atleast one neighboring basic service set. With reference to FIG. 1,neighboring BSS of access point 12 include the BSS of access point 14and/or the BSS of access point 16.

Returning to the logic diagram of FIG. 24, the process continues at step122 where the access point and/or the wireless communication devicedetermines whether the protocols of the wireless communication deviceswithin the proximal region are of a like protocol. The process thenproceeds to step 124 where the process branches depending on whether theprotocols of the wireless communication devices within the proximalregion are of a like protocol. When the wireless communication deviceswithin the proximal region all use the same protocol, the processproceeds to step 126 where the wireless communication devices use theirprotocol for setting up a wireless communication and for the wirelesscommunication.

If, however, at least one wireless communication device has a differentprotocol, the process proceeds to step 128 where the access point or awireless communication device selects a protocol of the protocols of thewireless communication devices within the proximal region based on aprotocol ordering to produce a selected protocol. The protocol orderingmay be an ordering of the protocols based on legacy ordering of wirelesscommunication devices and/or an ordering of the protocols based on atransmission efficiency ordering of the protocols. For example, IEEE802.11, IEEE 802.11b, IEEE 802.11g, and IEEE 802.11n compliant devicesoperate in the 2.4 GHz frequency band and IEEE 802.11a and IEEE 802.11ncompliant devices operate in the 4.9-5.85 GHz frequency band. Thus, inthe 2.4 GHz frequency band, if IEEE 802.11b stations are present withIEEE 802.11n device, MAC level protection mechanisms, such as thosedefined in IEEE 802.11g, and as shown in FIG. 6, may be used. However,if the only legacy IEEE.11g devices are present with IEEE 802.11ndevices, then either MAC level (e.g., FIG. 6) or PHY level (e.g., FIG.5) protection mechanisms may be used. In the 4.9-5.85 GHz frequencyband, if IEEE 802.11a devices are present with IEEE.11n devices, the MAClevel protection mechanism or the PHY level protection mechanism may beused.

As one of average skill in the art will appreciate, it may be moredesirable to use a PHY level protection mechanism, than a MAC levelprotection mechanism because the throughput impact will be less sincethe additional frames of the MAC level protection are not needed. Thus,when possible, the PHY mechanism should be employed first. If the PHYmechanism does not work well, as measured by the number ofunacknowledged frames exceeding a threshold, then the MAC levelmechanism should be employed.

As one of average skill in the art will further appreciate, the legacystatus and required use of protection mechanisms can be enabled in theERP Information Element of the beacon frame (and probe response frame).Currently IEEE 802.11g uses bits 0 to indicate Non-ERP (i.e. 0.11b)present and bit 1 to force stations to Use Protection (MAC level). Thiscan be extended to used the reserved bits (3 though 7) to indicatelegacy status of IEEE 802.11g or IEEE 802.11a stations. In oneembodiment, bit 3 may be used to indicate “Legacy OFDM present”. Thebits would then be interpreted as follows:

Bit 0 - Non ERP Bit 1 - Use Bit 3 - Legacy Present Protection OFDMPresent Action for 802.11n 0 0 0 Use .11n frames 1 1 0 Use MACprotection 1 1 1 Use MAC protection 0 1 1 Use PHY or MAC protection 0 01 Optionally use PHY or MAC ProtectionFor IEEE 802.11n the MAC level protection mechanisms are the same as forIEEE 802.11g. Stations should either use CTS to self or a CTS/RTSexchange to set the NAV (network allocation vector) of legacy stations.

Returning the logic diagram of FIG. 24, the processing continues at step130 where the wireless communication device utilizes the selectedprotocol within the proximal region to set up a wireless communicationwithin the proximal region. This was illustrated in the previousFigures. The process then proceeds to step 132 where the wirelesscommunication device uses its protocol for a data transmission of thewireless communication.

FIG. 25 is a logic diagram of method for determining whether theselected protocol should be changed. The processing begins at step 140where the access point and/or the wireless communication devices,monitors data transmissions within the proximal region forunacknowledged data transmissions. The process proceeds to step 142where the access point and/or the wireless communication device comparesthe unacknowledged data transmission with a transmission failurethreshold (e.g., up to 5%). If the comparison is favorable, the processproceeds to step 146 where the selected protocol remains unchanged andthe process repeats at step 140.

If, however, the comparison at step 144 was unfavorable, the processproceeds to step 148 where the access point and/or the wirelesscommunication device selects another one of the protocols of thewireless communication devices within the proximal region based on theprotocol ordering to produce another selected protocol. For example, theMAC layer protection mechanism may be selected to replace the PHY layerprotection mechanism when too many transmission failures occur. Theprocess then proceeds to step 150 where the wireless communicationdevice uses the another selected protocol within the proximal region toset up the wireless communication within the proximal region.

FIG. 26 is a logic diagram of a method for a wireless communicationdevice to participate in multiple protocol wireless communications. Theprocess begins at step 160 where the wireless communication deviceaffiliates with an access point utilizing a protocol (e.g., IEEE802.11n) of the wireless communication device. The process then proceedsto step 162 where the wireless communication device receives a selectedprotocol from the access point. Note that the selected protocol and theprotocol of the wireless communication device may be a wireless localarea network communication formats in accordance with IEEE 802.11, IEEE802.11a, IEEE 802.11b, IEEE 802.11g, IEEE 802.11n and/or furtherversions of the IEEE 802.11. Further note that the selected protocolincludes a first frame format that includes a legacy header and aMedia-Specific Access Control (MAC) layer partitioning field, a secondframe format that includes a physical (PHY) layer backward compatibleheader, and/or a third frame format that includes a current versionheader and the MAC layer partitioning field.

The process then proceeds to step 164 where the wireless communicationdevice determines whether the selected protocol and the protocol of thewireless communication device are of a like protocol. The processbranches at step 166 to step 168 when the protocols are the same and tostep 170 when the protocols are not the same. At step 168, the wirelesscommunication device utilizes the protocol to set up a wirelesscommunication and to transfer data. At step 170, the wirelesscommunication device utilizes the selected protocol to set up a wirelesscommunication. The process then proceeds to step 172 where the wirelesscommunication device utilizes the protocol of the wireless communicationdevice for the wireless communication.

FIG. 27 is a logic diagram of a method for a wireless communicationdevice to participate in multiple protocol wireless communications. Theprocess begins at step 180 where the wireless communication devicereceives a frame via a wireless channel. The process then proceeds tostep 182 where the wireless communication device determines whether aselected protocol is not of a like protocol of the wirelesscommunication device. When the selected protocol is the same as theprotocol of the wireless communication device, the process proceeds tostep 184 where the wireless communication device uses its protocol toset up a wireless communication and to transmit data.

If, however, the selected protocol is not the same as the protocol ofthe wireless communication device, the process proceeds to step 186where the wireless communication device uses the selected protocol tointerpret at least a portion of wireless communication set upinformation of the frame. In one embodiment, the wireless communicationdevice may interpret the set up information by interpreting a header ofthe frame for conformity with a legacy physical layer format to providethe interpreting of the at least a portion of the wireless communicationset up information and, when the header of the frame does not conformwith the legacy physical layer format, determining that the remainder ofthe frame is formatted in accordance with the protocol of the wirelesscommunication device. Note that the legacy physical layer formatincludes at least one of IEEE 802.11a and IEEE 802.11g and wherein theprotocol of the wireless communication device includes IEEE 802.11n.

In another embodiment, the wireless communication device may interpretthe set up information by interpreting the frame for conformity with alegacy Media-Specific Access Control (MAC) layer format to provide theinterpreting of the at least a portion of the wireless communication setup information and, when the header of the frame does not conform withthe legacy MAC layer format, determining that the remainder of the frameis formatted in accordance with the protocol of the wirelesscommunication device. Note that the legacy physical layer formatincludes at least one of IEEE 802.11a, IEEE 802.11b, and IEEE 802.11gand wherein the protocol of the wireless communication device includesIEEE 802.11n.

The process then proceeds to step 188 where the wireless communicationdevice, based on the interpreting of the at least a portion of thewireless communication set up information, determines whether aremainder of the frame is formatted in accordance with the protocol ofthe wireless communication device. The process then branches at step 190to step 194 when the remainder of the frame is formatted in accordancewith the protocol of the wireless communication device and to step 192when it does not. At step 192 the wireless communication device ignoresthe frame. At step 194, the wireless communication device processes theremainder of the frame based in accordance with the protocol of thewireless communication device.

FIG. 28 is a logic diagram of a method for a wireless communicationdevice to participate in multiple protocol wireless communications. Themethod begins at step 200 where the wireless communication devicedetermines whether a selected protocol is of a like protocol of thewireless communication device. The process branches at step 202 to step204 when the selected protocol is the protocol of the wirelesscommunication device and to step 206 when the protocols differ. At step204, the wireless communication device formats the set up informationportion of a frame and a data portion of the frame in accordance withits protocol. The wireless communication device then transmits theframe.

If, however, the selected protocol is not of the like protocol of thewireless communication device, the process proceeds to step 206 wherethe wireless communication device formats a portion of wirelesscommunication set up information in accordance with the selectedprotocol to produce legacy formatted set up information. The processthen proceeds to step 208 where the wireless communication deviceformats remainder of the wireless communication set up information inaccordance with the protocol of the wireless communication device toproduce current formatted set up information. The process then proceedsto step 210 where the wireless communication device formats data inaccordance with the protocol of the wireless communication device toproduce current formatted data. Refer to the previous Figures forexamples of such formatting. The process then proceeds to step 212 wherethe wireless communication device transmits a frame containing thelegacy formatted set up information, the current formatted set upinformation, and the current formatted data.

In an embodiment of the present invention, the preamble should bebackward compatible with existing IEEE 802.11 standards. An issue in TGnis how to interoperate with legacy IEEE 802.11a and IEEE 802.11b/gdevices, where interoperation includes two cases:

-   -   Same BSS: All devices communicating with the same AP.    -   Co-channel/“overlapping” BSS        Such can be addressed by either design the PLCP header to allow        an IEEE 802.11a/g STA to de-assert CCA or use a protection        mechanism like RTS/CTS or CTS-to-self.    -   IEEE 802.11g chose the latter in dealing with IEEE 802.11b        devices.    -   To some extent, RTS/CTS can be relied on to protect bursts        anyway.

For unchanged SIGNAL field decoding at legacy stations, it is desirableto use the same linear weighting of the existing long training andSIGNAL symbols at the transmitter antenna inputs. With a MISO system,the same weighting should be applied to the first two long trainingsymbols and the legacy SIGNAL field for decoding by legacy stations.

For the case of M transmitter antennas, N receiver antennas and asequence of L transmitted symbols, Xk is the received signal onsub-carrier k:

The zero-forcing (ZF) MIMO channel estimate is then computed as:

${\hat{H}}_{k} = {{( {S_{k}^{H} \cdot S_{k}} )^{- 1} \cdot S_{k}^{H} \cdot X_{k}} = {\frac{1}{M\;} \cdot S_{k}^{H} \cdot X_{k}}}$if the long training symbol sequence is defined well (i.e., Sk ends upbeing a real scalar times a unitary matrix).

The minimum mean-square error (MMSE) channel estimate is computed as:

Ĥ_(k) = (S_(k)^(H) ⋅ S_(k) + σ_(η)² ⋅ I)⁻¹ ⋅ S_(k)^(H) ⋅ X_(k) = ρ ⋅ S_(k)^(H) ⋅ X_(k)$\rho = \frac{1}{M + \sigma_{\eta}^{2}}$where, for simplicity, hk was assumed to be i.i.d. Gaussian and, again,use the “good long training choice”. Note that performance of the MMSEversus ZF estimation may be omitted for the sequences chosen in thefollowing, since S was carefully chosen as previously shown.

FIG. 29 is a diagram illustrating simultaneous second channel soundingwith a transmission model of the frame format 104 of FIG. 7. The frameformat 104 includes a carrier detect 225, channel sounding symbols 227,a signal field (SIG) 229, and a signal field (SIG 2) 231. By way ofexample, further frames are illustrated as formed via a multiple antennanext generation MIMO transmitter. These frames include carrier detect233, channel sounding symbols (2,2) 253, channel sounding (2,L) 237,signal field (SIG 2) 239, and carrier detect 241, channel sounding (M,2)243, channel sounding symbols (M,2) 245, and signal field (SIG 2) 247,which are discussed in additional detail with reference to FIGS. 30-32.The carrier detect 225, 233, and 241 are short symbols sent during a“Carrier Detect” period. “Carrier Detect” symbols for antennas 2 . . . Mare generally equivalent for as those transmitted on a first antenna,except cyclically shifted.

The first channel sounding symbols 227 and signal field (SIG) 229include the long training symbols and signal field of legacy systems,and are transmitted from a first antenna. These are used for computingan estimate of the channel from the first transmit antenna to thereceiver antennas. The second channel sounding symbols 235, 243, aretransmitted on antennas 2 . . . M and are used for computing an estimateof the channel from the second transmit antennas to the receiverantennas.

The signal fields (SIG 2) 239 and 247 includes the IEEE 802.11n rate andframe length information. Average output power is scaled to be constantthroughout the frame, averaged across the transmit antennas. For thistransmission format, in order to satisfy backwards compatibility issuesand also to satisfy the requirements of the next generation channelestimation requirements, a weighting factor W is chosen such that W andW−1 are simple to implement. Further, any beam forming issues from MIMOtransmitters (next generation devices) by [w11 . . . w1M] should bewell-received by legacy IEEE 802.11a/g devices.

In this embodiment, referring also to FIG. 30, which is another diagramof simultaneous second channel sounding, a channel sounding (S_(k)) 253is multiplied by a plurality of weighting factors (W_(k, m)) 301, 303,305, wherein k corresponds to the channel sounding number, which rangesfrom 1 to L, and M corresponds to the number of transmit antennas 82-86.The resulting weighted channel soundings are converted to RF signals viathe transmitters 67, 69, 71 and subsequently transmitted via theantennas 81, 83, 85. In such an embodiment, a weighting factor matrixmay be as follows:

$\begin{bmatrix}w_{11} & w_{12} & \ldots & w_{1,M} \\w_{21} & w_{22} & \ldots & w_{2,M} \\\vdots & \vdots & \ddots & \vdots \\w_{L\; 1} & w_{L\; 2} & \ldots & w_{LM}\end{bmatrix}s_{k}$With transmissions occurring on all antennas at all times, nulls may beformed. The nulls may be compensated for by selecting a weight sequencethat acts as a beam former such that the nulls are steered in particulardirections. For example, for the case of the vector w1=[1 1] (one row ofthe previous side's W matrix for a two-TX case), nulls would be steeredin the directions−90° and +90°. Thus, certain directions aredisadvantaged versus others at a single-input receiver of a legacy WLANdevice.

According to the present invention, a different complex weight isapplied to each subcarrier on M−1 of the transmit antennas. This forms adifferent beam pattern on each subcarrier and results in less power andcapacity loss in the worst directions. This is illustrated in FIGS. 31and 32.

FIG. 31 is a diagram illustrating the manner in which a preamble of theframe format of FIG. 7 is formed for a generalized next generation MIMOtransmitter and particularly for a two antenna next generation MIMOtransmitter. In this illustration, two preambles are generated: one foreach active antenna. The first preamble 311, which is transmitted by thefirst antenna, includes a double guard interval (GI2) 313, a firstchannel sounding (CS 0,0) 315, a second channel sounding (CS 0,1) 317, aguard interval (GI) 319, a signal field (SIG) 321, another guardinterval (GI) 323, and a third channel sounding (CS 0,2) 325. The secondpreamble 327, which is transmitted by the second antenna, includes adouble guard interval (GI2) 329, a first channel sounding (CS 1,0) 331,a second channel sounding (CS 1,1) 333, a guard interval (GI) 335, asignal field (SIG) 337, another guard interval (GI) 339, and a thirdchannel sounding (CS 1,2) 341.

In this embodiment, the following may be used for the various channelsoundings:S ₀₁ =S ₀₀S _(10,k) =−S _(00,k) ·e ^(i·θ) ^(k)S ₁₁ =S ₁₀S ₀₂ =S ₀₀S _(12,k) =S _(00,k) ·e ^(i·θ) ^(k)From these channel soundings, the weighting factor may be applied asfollows:

$S_{k} = {\begin{bmatrix}s_{10,k} & s_{11,k} \\s_{20,k} & s_{21,k}\end{bmatrix} = {{s_{00,k} \cdot \begin{bmatrix}1 & {- 1} \\1 & 1\end{bmatrix} \cdot \begin{bmatrix}1 & 0 \\0 & {\mathbb{e}}^{{\mathbb{i}} \cdot \theta_{k}}\end{bmatrix}} = \begin{bmatrix}s_{00,k} & {{- s_{00,k}} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot \theta_{k}}} \\s_{00,k} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot \theta_{k}}}\end{bmatrix}}}$where the first digital of the subscript of a channel soundingcorresponds to the number of antennas, the second digit corresponds tothe number of symbols, and the k corresponds to the number of channelsoundings. For example, S_(10, k) corresponds to the first symboltransmitted on the first antenna for the kth channel sounding.

To obtain a different beam pattern for each subcarrier, the following isapplied:

${\theta_{k} = {\pi \cdot {k/6}}},{k = {{- \frac{N_{subcarriers}}{2}}\ldots\frac{N_{subcarriers}}{2}}}$

FIG. 32 is a diagram illustrating the manner in which a preamble of theframe format of FIG. 7 is formed for a three antenna next generationMIMO transmitter. In this illustration, three preambles are generated:one for each active antenna. The first preamble 351, which istransmitted by the first antenna, includes a double guard interval (GI2)353, a first channel sounding (CS 0,0) 355, a second channel sounding(CS 0,1) 357, a guard interval (GI) 359, a signal field (SIG) 361,another guard interval (GI) 363, a third channel sounding (CS 0,2) 365,a third guard interval (GI) 367, and a fourth channel sounding (CS 0,3)369. The second preamble 371, which is transmitted by the secondantenna, includes a double guard interval (GI2) 373, a first channelsounding (CS 1,0) 375, a second channel sounding (CS 1,1) 377, a guardinterval (GI) 379, a signal field (SIG) 381, another guard interval (GI)383, a third channel sounding (CS 1,2) 385, a third guard interval (GI)387, and a fourth channel sounding (CS 1,3) 389. The third preamble 391,which is transmitted by the third antenna, includes a double guardinterval (GI2) 393, a first channel sounding (CS 2,0) 395, a secondchannel sounding (CS 2,1) 397, a guard interval (GI) 399, a signal field(SIG) 401, another guard interval (GI) 403, a third channel sounding (CS2,2) 405, a third guard interval (GI) 407, and a fourth channel sounding(CS 2,3) 409.

For the various channel soundings, the weighting factor matrix may beapplied as follows:

$S_{k} = {\begin{bmatrix}s_{10,k} & s_{11,k} & s_{12,k} \\s_{20,k} & s_{21,k} & s_{22,k} \\s_{30,k} & s_{31,k} & s_{32,k}\end{bmatrix} = \begin{bmatrix}s_{00,k} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot \theta_{k}}} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot \phi_{k}}} \\s_{00,k} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot {({\theta_{k}\frac{4 \cdot \pi}{3}})}}} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot {({\phi_{k}\frac{2 \cdot \pi}{3}})}}} \\s_{00,k} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot {({\theta_{k}\frac{2 \cdot \pi}{3}})}}} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot {({\phi_{k}\frac{4 \cdot \pi}{3}})}}}\end{bmatrix}}$To obtain a different beam pattern for each subcarrier, the following isapplied:θ_(k) =π·k/6φ_(k)=π·(k+4)/6

From FIGS. 31 and 32 more signal energy may be transmitted resulting inbetter channel estimates by the receiver. This enables a more simplifiedZF or MMSE channel estimation at Rx (mostly adds/shifts) in that:

$\mspace{20mu}{W_{T} = { \begin{bmatrix}{+ 1} & {- 1} \\{+ 1} & {+ 1}\end{bmatrix}\Rightarrow W_{T}^{- 1}  = {\frac{1}{2}\begin{bmatrix}{+ 1} & {- 1} \\{+ 1} & {+ 1}\end{bmatrix}}}}$ $W_{T} = { \begin{pmatrix}1 & 1 & 1 \\1 & \frac{{- 1} - {i \cdot \sqrt{3}}}{2} & \frac{{- 1} + {i \cdot \sqrt{3}}}{2} \\1 & \frac{{- 1} + {i \cdot \sqrt{3}}}{2} & \frac{{- 1} - {i \cdot \sqrt{3}}}{2}\end{pmatrix}\Rightarrow W_{T}^{- 1}  = {\frac{1}{3} \cdot \begin{pmatrix}1 & 1 & 1 \\1 & \frac{{- 1} + {i \cdot \sqrt{3}}}{2} & \frac{{- 1} - {i \cdot \sqrt{3}}}{2} \\1 & \frac{{- 1} - {i \cdot \sqrt{3}}}{2} & \frac{{- 1} + {i \cdot \sqrt{3}}}{2}\end{pmatrix}}}$The channel may be estimated with prior knowledge of the per-subcarrierbeamforming coefficients and then these coefficients do not need to beapplied to the remaining transmitted symbols. The advantage of this isthat no extra multiplications are required on the transmitter side, asthe LTRN sequence may simply be looked up in a table.

The channel may be estimated without knowledge of the per-subcarrierbeamforming coefficients and then these coefficients should be appliedto the remaining transmitted symbols. The advantage of this is that thereceiver channel estimation is simplified (fewer multiplies), but thetransmitter performs additional multiplications.

First case, using earlier notation and L=M:

${\hat{H}}_{k} = {\frac{1}{M} \cdot s_{00,k}^{*} \cdot W_{B,k}^{H} \cdot W_{T}^{H} \cdot X_{k}}$$W_{B,k} = {{diag}( \lbrack {1\mspace{14mu}{\mathbb{e}}^{\frac{{\mathbb{i}} \cdot \pi \cdot l_{1}}{6}}\ldots\mspace{14mu}{\mathbb{e}}^{\frac{{\mathbb{i}} \cdot \pi \cdot l_{M - 1}}{6}}} \rbrack )}$

Second case, using earlier notation and L=M:

${\hat{H}}_{k} = {\frac{1}{M} \cdot s_{00,k}^{*} \cdot W_{T}^{H} \cdot X_{k}}$Note that further refinement of the channel estimate is possible byduplicating the entire length-M sequence p times. The refinement may bemade by simple averaging. The overhead is identical to the single activetransmitter method described on slide 10, but the performance is farsuperior.

For the backward-compatible preamble case, in which the number of longtraining symbols is M+1, the longer sequence would consist of p*M+1 longtraining symbols. There are p identical blocks of M symbols, and thefirst and second symbols on each antenna are identical.

As one of average skill in the art will appreciate, the term“substantially” or “approximately”, as may be used herein, provides anindustry-accepted tolerance to its corresponding term. Such anindustry-accepted tolerance ranges from less than one percent to twentypercent and corresponds to, but is not limited to, component values,integrated circuit process variations, temperature variations, rise andfall times, and/or thermal noise. As one of average skill in the artwill further appreciate, the term “operably coupled”, as may be usedherein, includes direct coupling and indirect coupling via anothercomponent, element, circuit, or module where, for indirect coupling, theintervening component, element, circuit, or module does not modify theinformation of a signal but may adjust its current level, voltage level,and/or power level. As one of average skill in the art will alsoappreciate, inferred coupling (i.e., where one element is coupled toanother element by inference) includes direct and indirect couplingbetween two elements in the same manner as “operably coupled”. As one ofaverage skill in the art will further appreciate, the term “comparesfavorably”, as may be used herein, indicates that a comparison betweentwo or more elements, items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signal1 has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1.

The preceding discussion has presented various embodiments for wirelesscommunications in a wireless communication system that includes aplurality of wireless communication devices of differing protocols. Asone of average skill in the art will appreciate, other embodiments maybe derived from the teachings of the present invention without deviatingfrom the scope of the claims.

Mode Selection Tables

TABLE 1 2.4 GHz, 20/22 MHz channel BW, 54 Mbps max bit rate Code RateModulation Rate NBPSC NCBPS NDBPS EVM Sensitivity ACR AACR 1 Barker BPSK2 Barker QPSK 5.5 CCK 6 BPSK 0.5 1 48 24 −5 −82 16 32 9 BPSK 0.75 1 4836 −8 −81 15 31 11 CCK 12 QPSK 0.5 2 96 48 −10 −79 13 29 18 QPSK 0.75 296 72 −13 −77 11 27 24 16-QAM 0.5 4 192 96 −16 −74 8 24 36 16-QAM 0.75 4192 144 −19 −70 4 20 48 64-QAM 0.666 6 288 192 −22 −66 0 16 54 64-QAM0.75 6 288 216 −25 −65 −1 15

TABLE 2 Channelization for Table 1 Frequency Channel (MHz) 1 2412 2 24173 2422 4 2427 5 2432 6 2437 7 2442 8 2447 9 2452 10 2457 11 2462 12 2467

TABLE 3 Power Spectral Density (PSD) Mask for Table 1 PSD Mask 1Frequency Offset dBr −9 MHz to 9 MHz 0 +/−11 MHz −20 +/−20 MHz −28 +/−30MHz and −50 greater

TABLE 4 5 GHz, 20 MHz channel BW, 54 Mbps max bit rate Code RateModulation Rate NBPSC NCBPS NDBPS EVM Sensitivity ACR AACR 6 BPSK 0.5 148 24 −5 −82 16 32 9 BPSK 0.75 1 48 36 −8 −81 15 31 12 QPSK 0.5 2 96 48−10 −79 13 29 18 QPSK 0.75 2 96 72 −13 −77 11 27 24 16-QAM 0.5 4 192 96−16 −74 8 24 36 16-QAM 0.75 4 192 144 −19 −70 4 20 48 64-QAM 0.666 6 288192 −22 −66 0 16 54 64-QAM 0.75 6 288 216 −25 −65 −1 15

TABLE 5 Channelization for Table 4 Frequency Frequency Channel (MHz)Country Channel (MHz) Country 240 4920 Japan 244 4940 Japan 248 4960Japan 252 4980 Japan 8 5040 Japan 12 5060 Japan 16 5080 Japan 36 5180USA/Europe 34 5170 Japan 40 5200 USA/Europe 38 5190 Japan 44 5220USA/Europe 42 5210 Japan 48 5240 USA/Europe 46 5230 Japan 52 5260USA/Europe 56 5280 USA/Europe 60 5300 USA/Europe 64 5320 USA/Europe 1005500 USA/Europe 104 5520 USA/Europe 108 5540 USA/Europe 112 5560USA/Europe 116 5580 USA/Europe 120 5600 USA/Europe 124 5620 USA/Europe128 5640 USA/Europe 132 5660 USA/Europe 136 5680 USA/Europe 140 5700USA/Europe 149 5745 USA 153 5765 USA 157 5785 USA 161 5805 USA 165 5825USA

TABLE 6 2.4 GHz, 20 MHz channel BW, 192 Mbps max bit rate TX ST Anten-Code Code Rate nas Rate Modulation Rate NBPSC NCBPS NDBPS 12 2 1 BPSK0.5 1 48 24 24 2 1 QPSK 0.5 2 96 48 48 2 1 16-QAM 0.5 4 192 96 96 2 164-QAM 0.666 6 288 192 108 2 1 64-QAM 0.75 6 288 216 18 3 1 BPSK 0.5 148 24 36 3 1 QPSK 0.5 2 96 48 72 3 1 16-QAM 0.5 4 192 96 144 3 1 64-QAM0.666 6 288 192 162 3 1 64-QAM 0.75 6 288 216 24 4 1 BPSK 0.5 1 48 24 484 1 QPSK 0.5 2 96 48 96 4 1 16-QAM 0.5 4 192 96 192 4 1 64-QAM 0.666 6288 192 216 4 1 64-QAM 0.75 6 288 216

TABLE 7 Channelization for Table 6 Channel Frequency (MHz) 1 2412 2 24173 2422 4 2427 5 2432 6 2437 7 2442 8 2447 9 2452 10 2457 11 2462 12 2467

TABLE 8 5 GHz, 20 MHz channel BW, 192 Mbps max bit rate TX ST Anten-Code Code Rate nas Rate Modulation Rate NBPSC NCBPS NDBPS 12 2 1 BPSK0.5 1 48 24 24 2 1 QPSK 0.5 2 96 48 48 2 1 16-QAM 0.5 4 192 96 96 2 164-QAM 0.666 6 288 192 108 2 1 64-QAM 0.75 6 288 216 18 3 1 BPSK 0.5 148 24 36 3 1 QPSK 0.5 2 96 48 72 3 1 16-QAM 0.5 4 192 96 144 3 1 64-QAM0.666 6 288 192 162 3 1 64-QAM 0.75 6 288 216 24 4 1 BPSK 0.5 1 48 24 484 1 QPSK 0.5 2 96 48 96 4 1 16-QAM 0.5 4 192 96 192 4 1 64-QAM 0.666 6288 192 216 4 1 64-QAM 0.75 6 288 216

TABLE 9 channelization for Table 8 Frequency Frequency Channel (MHz)Country Channel (MHz) Country 240 4920 Japan 244 4940 Japan 248 4960Japan 252 4980 Japan 8 5040 Japan 12 5060 Japan 16 5080 Japan 36 5180USA/Europe 34 5170 Japan 40 5200 USA/Europe 38 5190 Japan 44 5220USA/Europe 42 5210 Japan 48 5240 USA/Europe 46 5230 Japan 52 5260USA/Europe 56 5280 USA/Europe 60 5300 USA/Europe 64 5320 USA/Europe 1005500 USA/Europe 104 5520 USA/Europe 108 5540 USA/Europe 112 5560USA/Europe 116 5580 USA/Europe 120 5600 USA/Europe 124 5620 USA/Europe128 5640 USA/Europe 132 5660 USA/Europe 136 5680 USA/Europe 140 5700USA/Europe 149 5745 USA 153 5765 USA 157 5785 USA 161 5805 USA 165 5825USA

TABLE 10 5 GHz, with 40 MHz channels and max bit rate of 486 Mbps TX STCode Code Rate Antennas Rate Modulation Rate NBPSC 13.5 Mbps 1 1 BPSK0.5 1 27 Mbps 1 1 QPSK 0.5 2 54 Mbps 1 1 16-QAM 0.5 4 108 Mbps 1 164-QAM 0.666 6 121.5 Mbps 1 1 64-QAM 0.75 6 27 Mbps 2 1 BPSK 0.5 1 54Mbps 2 1 QPSK 0.5 2 108 Mbps 2 1 16-QAM 0.5 4 216 Mbps 2 1 64-QAM 0.6666 243 Mbps 2 1 64-QAM 0.75 6 40.5 Mbps 3 1 BPSK 0.5 1 81 Mbps 3 1 QPSK0.5 2 162 Mbps 3 1 16-QAM 0.5 4 324 Mbps 3 1 64-QAM 0.666 6 365.5 Mbps 31 64-QAM 0.75 6 54 Mbps 4 1 BPSK 0.5 1 108 Mbps 4 1 QPSK 0.5 2 216 Mbps4 1 16-QAM 0.5 4 432 Mbps 4 1 64-QAM 0.666 6 486 Mbps 4 1 64-QAM 0.75 6

TABLE 11 Power Spectral Density (PSD) mask for Table 10 PSD Mask 2Frequency Offset dBr −19 MHz to 19 MHz 0 +/−21 MHz −20 +/−30 MHz −28+/−40 MHz and −50 greater

TABLE 12 Channelization for Table 10 Frequency Frequency Channel (MHz)Country Channel (MHz) County 242 4930 Japan 250 4970 Japan 12 5060 Japan38 5190 USA/Europe 36 5180 Japan 46 5230 USA/Europe 44 5520 Japan 545270 USA/Europe 62 5310 USA/Europe 102 5510 USA/Europe 110 5550USA/Europe 118 5590 USA/Europe 126 5630 USA/Europe 134 5670 USA/Europe151 5755 USA 159 5795 USA

1. A method for generating a preamble of a frame for a multiple inputmultiple output (MIMO) wireless communication, the method comprises: foreach transmit antenna of the MIMO wireless communication, generating acarrier detect field, wherein, for a first grouping of the transmitantennas of the MIMO wireless communication: generating a first guardinterval following the carrier detect field; generating at least onechannel sounding field with respect to each transmit antennas of thefirst grouping, wherein the at least one channel sounding field followsthe first guard interval; and for each transmit antenna of the firstgrouping, applying a cyclic shift to the at least one channel soundingfield prior to transmission; and when the MIMO wireless communicationincludes more than the first grouping of the transmit antennas, foranother grouping of the transmit antennas: generating at least one otherchannel sounding field for each transmit antenna of the anothergrouping, wherein, from transmit antenna to transmit antenna in theanother grouping, the at least one other channel sounding field followsthe at least one channel sounding field; and generating the first guardinterval prior to the at least one other channel sounding field; and foreach transmit antenna of the another grouping, applying another cyclicshift to the at least one other channel sounding field prior totransmission of the another grouping.
 2. The method of claim 1 furthercomprises, for each transmit antenna of the first grouping of thetransmit antennas of the MIMO wireless communication: generating asecond guard interval following the at least one channel sounding field;and generating a signal field following the second guard interval. 3.The method of claim 2 further comprises, for each transmit antenna ofthe another grouping of the transmit antennas: generating a third guardinterval preceding the at least one other channel sounding field,wherein the first and third guard intervals are greater in duration thanthe second guard interval.
 4. The method of claim 1, wherein thegenerating the carrier detect field comprises: generating a shorttraining sequence in accordance with a legacy protocol is based on anumber of the transmit antennas and duration of the short trainingsequence.
 5. The method of claim 4 further comprises, when the number oftransmit antennas is three: for the first grouping of the transmitantennas of the MIMO wireless communication, generating a first andsecond long training sequence in accordance with the legacy protocol asat least one channel sounding field, wherein the first grouping includestwo of the three transmit antennas; and generating a third long trainingsequence in accordance with the legacy protocol as the at least oneother channel sounding field for the another grouping of the transmitantennas, wherein the another grouping includes a third of the threetransmit antennas.
 6. The method of claim 4 further comprises, when thenumber of transmit antennas is four: for the first grouping of thetransmit antennas of the MIMO wireless communication, generating a firstand second long training sequence in accordance with the legacy protocolas at least one channel sounding field, wherein the first groupingincludes two of the four transmit antennas; and generating third andfourth long training sequences in accordance with the legacy protocol asat least one other channel sounding field for the another grouping ofthe transmit antennas, wherein the another grouping includes another twoof the four transmit antennas.
 7. The method of claim 1 furthercomprises for each of the transmit antennas of the MIMO wirelesscommunication: generating another guard interval following the at leastone other channel sounding field; and generating a second signal fieldfollowing the another guard interval.
 8. A method for generating alegacy compatible preamble of a frame for a multiple input multipleoutput (MIMO) wireless communication, the method comprises: for eachtransmit antenna of a plurality of transmit antennas for the MIMOwireless communication, generating a carrier detect field, wherein, fora first transmit antenna of the plurality of transmit antennas:generating a first guard interval following the carrier detect field;generating a first channel sounding field following the first guardinterval; generating a second channel sounding field following the firstchannel sounding field; and for each transmit antenna of a firstgrouping of remaining transmit antennas of the plurality of transmitantennas: generating a third channel sounding field; generating a fourthchannel sounding field following the third channel sounding field;generating a second guard interval preceding the third channel soundingfield; and applying a cyclic shift to the carrier detect field prior totransmission via the each transmit antenna of the first transmit antennaand of the first grouping of the remaining transmit antennas.
 9. Themethod of claim 8, wherein when the plurality of transmit antennasincludes four transmit antennas: for a fourth transmit antenna of theplurality of transmit antennas: generating a fifth channel soundingfield; generating a sixth channel sounding field following the fifthchannel sounding field; and generating a third guard interval precedingthe fifth channel sounding field.
 10. The method of claim 9 furthercomprises for each of the plurality of transmit antennas: generatinganother guard interval following the sixth channel sounding field; andgenerating a signal field following the second guard interval.
 11. Themethod of claim 8 further comprises, for the first transmit antenna:generating another guard interval following the second channel soundingfield; and generating a signal field following the second guardinterval.
 12. The method of claim 8, wherein the generating the carrierdetect field comprises: generating a short training sequence inaccordance with a legacy protocol is based on a number of the transmitantennas and duration of the short training sequence.
 13. The method ofclaim 8 further comprises for each of the transmit antennas of the MIMOwireless communication: generating another guard interval following thefourth channel sounding field; and generating a second signal fieldfollowing the another guard interval.
 14. A radio frequency (RF)transmitter comprises: a baseband processing module configured toproduce outbound symbol streams from outbound data; and a transmittersection configured to produce outbound RF signals from the outboundsymbol streams, wherein the baseband processing module is operable to:for each transmit antenna of the transmitter section, generate a carrierdetect field, wherein, from transmit antenna to transmit antenna for afirst grouping of the transmit antennas of the transmitter section:generate a first guard interval following the carrier detect field;generate at least one channel sounding field, wherein, from transmitantenna to transmit antenna in the first grouping, wherein the at leastone channel sounding field follows the first guard interval; and foreach transmit antenna of the first grouping, applying a cyclic shift tothe carrier detect field prior to transmission; and when the transmittersection includes more than the first grouping of the transmit antennas,for another grouping of the transmit antennas: generate at least oneother channel sounding field, wherein, from transmit antenna to transmitantenna in the another grouping, wherein the at least one other channelsounding field follows the at least one channel sounding field; andgenerate the first guard interval prior to the at least one otherchannel sounding field; and for each transmit antenna of the anothergrouping, applying another cyclic shift to the carrier detect fieldprior to transmission of the another grouping.
 15. The RF transmitter ofclaim 14, wherein the baseband processing module is further operable to,for each antenna of the first grouping of the transmit antennas of thetransmitter section: generate a second guard interval following the atleast one channel sounding field; and generate a signal field followingthe second guard interval.
 16. The RF transmitter of claim 15, whereinthe baseband processing module is further operable to, for each antennaof the another grouping of the transmit antennas: generate a third guardinterval preceding the at least one other channel sounding field,wherein the first and third guard intervals are greater in duration thanthe second guard interval.
 17. The RF transmitter of claim 14, whereinthe baseband processing module is further operable to generate thecarrier detect field by: generating a short training sequence inaccordance with a legacy protocol based on a number of the transmitantennas and a duration of the short training sequence.
 18. The RFtransmitter of claim 17, wherein the baseband processing module isfurther operable to, when the number of transmit antennas is three: forthe first grouping of the transmit antennas of the transmitter section,generate a first and second long training sequence in accordance withthe legacy protocol as at least one channel sounding field, wherein thefirst grouping includes two of the three transmit antennas; and generatea third long training sequence in accordance with the legacy protocol asthe at least one other channel sounding field for the another groupingof the transmit antennas, wherein the another grouping includes a thirdof the three transmit antennas.
 19. The RF transmitter of claim 17,wherein the baseband processing module is further operable to, when thenumber of transmit antennas is four: for the first grouping of thetransmit antennas of the transmitter section, generate a first andsecond long training sequence in accordance with the legacy protocol asat least one channel sounding field, wherein the first grouping includestwo of the four transmit antennas; and generate third and fourth longtraining sequences in accordance with the legacy protocol as at leastone other channel sounding field for the another grouping of thetransmit antennas, wherein the another grouping includes another two ofthe four transmit antennas.
 20. The RF transmitter of claim 14, whereinan amount of the cyclic shift per antenna is based upon a total numberof the transmit antennas.